Genetics (Griffiths 9E)

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One of two purine nitrogenous bases in DNA and RNA.

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adenine

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A three-base sequence on one loop of a transfer RNA molecule that is complementary to an mRNA codon, and therefore brings together the appropriate amino acid and its mRNA instructions.

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anticodon

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Computational information systems and analytical methods applied to biological problems such as genomic analysis

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bioinformatics

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Analysis of the relations of the genome sequences of two or more species

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comparative genomics

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The pairs of DNA bases that bond together; adenine hydrogen bonds to thymine and guanine to cytosine in the DNA double helix.

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complementary base pairs

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The genetic material. The biochemical that forms genes

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deoxyribonucleic acid (DNA)

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Variation in the outcome of development as a consequence of random events in cell division, cell movement, and small differences in the number and location of molecules within cells

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developmental noise

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A cell containing two sets of chromosomes.

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diploid cell

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A complex cell containing organelles, including a nucleus

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eukaryotic cell

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The classical approach to genetic analysis, in which genes are first identified by mutant alleles and mutant phenotypes and later cloned and subjected to molecular analysis

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forward genetics

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A sequence of DNA that instructs a cell to produce a particular protein

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gene

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Naturally occurring genetic differences between individual members of a population

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genetic polymorphism

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The study of inherited variation

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genetics

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All the genetic material in the cells of a particular type of organism

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genome

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The study of the functions and interactions of many genes at a time

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genomics

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The allele combinations in an individual that cause a particular trait or disorder

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genotype

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One of the two purine nitrogenous bases in DNA and RNA

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guanine

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A cell containing one set of chromosomes (half the number of chromosomes of a somatic cell)

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haploid (cell)

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A molecule of RNA complementary in sequence to the coding strand of a gene. Messenger RNA carries the information that specifies a particular protein product

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messenger RNA (mRNA)

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A species chosen for use in studies of genetics because it is well suited to the study of one or more genetic processes

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model organism

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An allele that differs from the normal or most common allele, altering the phenotype

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mutant

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A change in a gene's biochemical makeup; a change in DNA

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mutation

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The transfer of electrophoretically separated RNA molecules from a gel onto an absorbent sheet, which is then immersed in a labeled probe that will bind to the RNA of interest

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Northern blotting

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The building block of a nucleic acid, consisting of a phosphate group, a nitrogenous base, and a 5-carbon sugar

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nucleotide

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The nitrogen base (a purine or pyrimidine group) that forms part of a nucleotide

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nucleotide base

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The expression of a gene in traits or symptoms

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phenotype

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The most extensively used method for detecting specific macromolecules: a mixture of macromolecules (DNA, RNA, or protein) is exposed to a molecule - the probe - that will bind only with the sought-after macromolecule

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probing

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A simple cell bound by a cell membrane, and sometimes a cell wall, that contains ribosomes and sometimes membranes, but no other organelles and no nucleus. Bacteria and archaea are prokaryotes

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prokaryotic cell

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A type of macromolecule that is the direct product of genetic information; a chain of amino acids

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protein

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An enzyme, derived from bacteria, that cuts DNA at certain sequences

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restriction enzyme

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An experimental procedure that begins with a cloned segment of DNA or a protein sequence and uses it (through directed mutagenesis) to introduce programmed mutations back into the genome to investigate function

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reverse genetics

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A nucleic acid whose sequence of building blocks represents a gene's sequence (mRNA), or that assists protein synthesis (tRNA and rRNA)

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ribonucleic acid (RNA)

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An organelle consisting of RNA and protein that is a scaffold for protein synthesis

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ribosome

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The transfer of electrophoretically separated fragments of DNA from a gel to an absorbent sheet such as paper; this sheet is then immersed in a solution containing a labeled probe that will bind to a fragment of interest

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Southern blot

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One of the two pyrimidine bases in DNA

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thymine

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The RNA molecule copied from the DNA template strand by RNA polymerase

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transcript

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Manufacturing RNA from DNA

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transcription

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A type of RNA that connects mRNA to amino acids during protein synthesis

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transfer RNA (tRNA)

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Assembly of an amino acid chain according to the sequence of base triplets in a molecule of mRNA

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translation

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An infectious particle built of nucleic acid in a protein coat.

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virus

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Membrane carrying an imprint of proteins separated by electrophoresis. Can be probed with a labeled antibody to detect a specific protein

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Western blot

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The genotype or phenotype that is found in nature or in the standard laboratory stock for a given organism

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wild type

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An alternate form of a gene.

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allele

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In a fungus, a sac that encloses a tetrad or an octad of ascospores

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ascus

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Two homologous chromosomes paired at meiosis

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bivalent

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The largest constriction in a chromosome, located at a specific site in each chromosome type.

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centromere

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An attribute of individual members of a species for which various heritable differences can be defined

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character

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A single, very long DNA molecule and its associated proteins forming half of a replicated chromosome.

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chromatid

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DNA and its associated histone proteins.

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chromatin

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Transverse stripes on the chromosomes of many organisms, revealed by special staining procedures

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chromosomal band

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A linear end-to-end arrangement of genes and other DNA, sometimes with associated protein and RNA

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chromosome

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The deliberate mating of two parental types of organisms in genetic analysis

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cross

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A polymorphism with only two forms

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dimorphism

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A plant species in which male and female organs are on separate plants

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dioecious plant

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A cell having two chromosome sets or an individual organism having two chromosome sets in each of its cells

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diploid

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A gene variant expressed when present in even one copy.

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dominant

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A pair of sister chromatids joined at the centromere, as in the first division of meiosis

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dyad

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Chromosomes that do not stain. It contains active genes

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euchromatin

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The progeny individuals arising from a cross of two homozygous diploid lines

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first filial generation (F1)

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The process whereby geneticists find a set of genes affecting some biological process of interest by the single-gene inheritance patterns of their mutant alleles or by genomic analysis

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gene discovery

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The two copies of a particular type of gene present in a diploid cell (one in each chromosome set)

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gene pair

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The use of recombination and mutation to piece together the various components of a given biological function

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genetic dissection

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A cell having one chromosome set or an organism composed of such cells

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haploid

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The number of chromosomes in the basic genomic set of a species

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haploid number

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A gene that does not provied enough gene product (generally a protein) to carry out the normal transactions of the cell in a heterozygote

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haploinsufficient

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Describes a gene that, in a diploid cell, can promote wild-type function in only one copy (dose)

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haplosufficient

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The sex that has half as many X-linked genes as the other sex; a human male

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hemizygous

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Dark-staining genetic material that is inactive but that maintains the chromosome's structural integrity

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heterochromatin

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The sex that has heteromorphic sex chromosomes (e.g., XY) and hence produces two different kinds of gametes with respect to the sex chromosomes

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heterogametic sex

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An individual organism having a heterozygous gene pair

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heterozygote

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Having two different alleles of a gene

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heterozygous

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The sex with identical types of sex chromosomes; the human female

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homogametic sex

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A member of a pair of homologous chromosomes

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homolog

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Chromosomes that pair with each other at meiosis or chromosomes in different species that have retained most of the same genes during their evolution from a common ancestor

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homologous chromosome

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An individual organism that is homozygous

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homozygote

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Refers to a genotype such as A / A

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homozygous dominant

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Refers to a genotype such as a / a

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homozygous recessive

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Base sequences within a gene that are transcribed but are excised from the mRNA before translation into protein. Introns are interspersed with protein-encoding exons

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introns

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A complex of proteins to which a nuclear spindle fiber attaches

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kinetochore

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The distribution of alleles of a gene into separate gametes during meiosis. Mendel's first law.

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law of equal segregation (Mendel's First Law)

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A mutation that confers a mutant phenotype but still retains a low but detectable level of wild-type function

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leaky mutation

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A cell in which meiosis takes place

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meiocyte

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Two successive nuclear divisions (with corresponding cell divisions) that produce gametes (in animals) or sexual spores (in plants and fungi) that have one-half of the genetic material of the original cell

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meiosis

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Division of somatic (nonsex) cells

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mitosis

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A single-locus heterozygote of the type A / a

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monohybrid

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A cross between two individuals identically heterozygous at one gene pair -- for example, A / a X A / a

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monohybrid cross

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One form of a genetic polymorphism; the morph can be either a phenotype or a molecular sequence

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morph

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An organism or cell carrying a mutation

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mutant

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A region (or regions) of the chromosome set that is physically associated with the nucleolus and contains rRNA genes

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nucleolar organizer

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A structure within the nucleus where ribosomes are assembled from ribosomal RNA and protein

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nucleolus

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The basic unit of eukaryotic chromosome structure; a ball of eight histone molecules that is wrapped by two coils of DNA

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nucleosome

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An allele whose effect is the absence either of normal gene product at the molecular level or of normal function at the phenotypic level

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null allele

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The two strains or individual organisms that constitute the start of a genetic breeding experiment; their progeny constitute the F1 generation

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parental generation

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Deducing single-gene inhereitance of human phenotypes by a study of the progeny of matings within a family, often stretching back several generations

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pedigree analysis

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A DNA sequence at a certain chromosomal locus that varies in at least one percent of individuals in a population

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polymorphism

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One of the (usually four) cells formed by the two meiotic divisions

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product of meiosis

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The probability of two independent events occurring simultaneously is the product of the individual probabilities

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product rule

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A characteristic feature of an organism, such as size, color, shape, or enzyme activity

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property

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In a human pedigree, the person who first came to the attention of the geneticist

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propositus

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Genes on the tips of the Y chromosome that have counterparts on the X chromosome

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pseudoautosomal region

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A population of individuals all bearing the identical fully homozygous genotype

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pure line

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An allele whose expression is masked by another allele

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recessive

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The progeny of a cross between two individuals from the F1 generation

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second filial generation (F2)

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To fertilize eggs with sperms from the same individual

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self

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A chromosome containing genes that specify sex. A human male has one X and one Y chromosome; a female has two X chromosomes

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sex chromosome

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The location of a gene on a sex chromosome

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sex linkage

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The maleness gene, residing on the Y chromosome

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SRY gene

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A chromosome tip

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telomere

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Crossing an individual of unknown genotype to an individual who is homozygous recessive for the trait being studies

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test cross

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An individual organism homozygous for one or more recessive alleles; used in a testcross

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tester

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(1) Four homologous chromatids in a bundle in the first meiotic prophase and metaphase (2) The four haploid product cells from a single meiosis

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tetrad

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More or less synonymous with phenotype

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trait

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A general term for any genetic unit that can insert into a chromosome, excise, and reinsert elsewhere; includes insertion sequences and transposons

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transposable element

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One of a pair of sex chromosomes, distinguished from the Y chromosome

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X chromosome

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The inheritance pattern of genes found on the X chromosome but not on the Y chromosome

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X linkage

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One of a pair of sex chromosomes, distinguished from the X chromosome

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Y chromosome

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The inheritance pattern of genes found on the Y chromosome but not on the X chromosome

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Y linkage

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A prenatal human from the fertilized ovum stage until formation of the primordial embryo, at about two weeks.

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zygote

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A statistical test used to determine the probability of obtaining observed proportions by chance, under a specific hypothesis

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chi-square test

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The small genomic component found in the chloroplasts of plants, concerned with photosynthesis and other functions taking place within that organelle

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chloroplast DNA (cpDNA)

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Segregation in which genetically different daughter cells arise from a progenitor that is a cytohet

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cytoplasmic segregation

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A double heterozygote such as A / a - B / b

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dihybrid

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A cross of individuals who are heterozygous for two traits.

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dihybrid cross

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A situation in which an F1 is larger or healthier than its two different pure parental lines

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hybrid vigor

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The random arrangement of homologous chromosome pairs, in terms of maternal or paternal origin, down the center of a cell in metaphase I. The consequence is that inheritance of a gene one chromosome does not influence inheritance of a gene on a different chromosome

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independent assortment

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A type of uniparental inheritance in which all progeny have the genotype and phenotype of the parent acting as the female

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maternal inheritance

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Recombination from assortment or crossing over at meiosis

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meiotic recombination

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The law of independent assortment; unlinked or distantly linked segregating gene pairs assort independently at meiosis

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Mendel's Second Law

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The subset of the genome found in the mitochondrion, specializing in providing some of the organelle's functions

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mitochondrial DNA (mtDNA)

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A hypothesis that explains quantitative variation by assuming the interaction of a large number of genes (polygenes), wach with a small additive effect on the character

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polygene (quantitative trait locus)

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A gene affecting the phenotypic variation in continuously varying traits such as height and weight, among others

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quantitative trait locus (QTL)

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A series of alleles on a chromosome that differs from the series of either parent

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recombinant

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(1) In general, any process in a diploid or partly diploid cell that generates new gene or chromosomal combinations not previously found in that cell or in its progenitors (2) At meiosis, the process that generates a haploid product of meiosis whose genotype is different from either of the two haploid genotypes that constrituted the meiotic diploid

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recombination

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The probability that one or the other of two mutually exclusive events will occur is the sum of their individual probabilities

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sum rule

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aka map unit; The "distance" between two linked gene pairs where 1 percent of the products of meiosis are recombinant; a unit of distance in a linkage map

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centimorgan (cM)

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A representation of all chromosomes in the genome as lines, marked with the positions of genes known from their mutant phenotypes, plus molecular markers. Based on analysis of recombinant frequency

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chromosome map

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In a heterozygote having two mutant sites within a gene or within a gene cluster, the arrangement A1A2/a1a2

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cis conformation

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The ratio of the observed number of double recombinants to the expected number

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coefficient of coincidence (coc)

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An event during prophase I when homologs exchange parts, adding to genetic variability.

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crossing over

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Meiotic product cells with chromosomes that have engaged in a crossover

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crossover product

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The autoradiographic banding pattern produced when DNA is digested with a restriction enzyme that cuts outside a family of VNTRs (variable number of tandem repeats) and a Southern blot of the electrophoretic gel is probed with a VNTR-specific probe. Unlike true fingerprintes, these patterns are not unique to each individual organism

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DNA fingerprint

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A linear pattern of spore phenotypes within an ascus for a particular allele pair, produced when the alleles go into separate nuclei at the first meiotic division, showing that no crossover has taken place between the allele pair and the centromere

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first-division segregation pattern (MI pattern)

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A distance on the chromosome map corresponding to 1 percent recombinant frequency

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genetic map unit (mu)

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A series of known DNA sequences linked on a chromosome

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haplotype

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A measure of the independence of crossovers from each other, calculated by subtracting the coefficient of coincidence from 1

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interference

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Extremely tight linkage between two genetic loci, typically a marker and a disease-causing allele

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linkage disequilibrium

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A chromosome map; an abstract map of chromosomal loci that is based on recombinant frequencies

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linkage map

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The situation in which two genes are on the same chromosome as decued by recombinant frequencies less than 50 percent

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linked genes

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A statistical measurement that indicates whether DNA sequences are usually inherited together due to linkage or chance

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LOD score

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A formula expressing the relation between distance in a linkage map and recombinant frequency

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mapping function

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A difference in DNA at the same locus in two genomes that is due to different repeat lengths of a microsatellite

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microsatellite marker

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Heterozygous locus representing a variable number of tendem repeats of a unit 15 - 100 nucleotides long

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minisatellite marker

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A site of DNA heterzygosity, not necessarily associated with phenotypic variation, used as a tag for a particular chromosomal locus

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molecular marker

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A hypothesis that proposes no difference between two or more data sets

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null hypothesis

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An ascus containing eight ascospores, produced in species in which the tetrad normally undergoes a postmeiotic mitotic division

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octad

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The ordered and oriented map of cloned DNA gragments on the genome

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physical map

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A mathematical expression giving the probability of observing various numbers of a particular event in a sample when the mean probability of an event on any one trial is very small

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Poisson distribution

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The proportion (or percentage) of recombinant cells or individuals

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recombinant frequency (RF)

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A chromosome map in which the positions of loci shown are based on recombinant frequencies

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recombination map

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Difference in restriction enzyme cutting sites among individuals at the same site among the chromosomes, resulting in different patterns of DNA fragment sizes

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restriction fragment length polymorphism (RFLP)

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A pattern of ascospore genotypes for a gene pair showing that the two alleles separate into different nuclei only at the second meiotic division, as a result of a crossover between that gene pair and its centromere; can be detected only in a linear ascus

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second-division segregation pattern (MII)

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The existence in the population of individuals showing different numbers of copies of a short simple DNA sequence at one chromosomal locus

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simple sequence length polymorphism (SSLP)

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A nucleotide-pair difference at a given location in the genomes of two or more naturally occurring individuals

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single nucleotide polymorphism (SNP)

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A testcross in which one parent has three heterozygous gene pairs

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three-point testcross

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In a heterozygote with two mutant sites within a gene or gene cluster, the arrangement a1 + / + a2

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trans conformation

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A chromosomal locus at which a particular repetitive sequence is present in different numbers in different individuals or in the two different homologs in one diploid individual

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variable number tandem repeat (VNTR)

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Region at which prophage integrates

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attachment site

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A strain of microorganisms that will proliferate only when the medium is supplemented with a specific substance not required by wild-type organisms (compare prototroph)

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auxotroph

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A virus that infects bacteria

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bacteriophage (phage)

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Members of a colony that have a single genetic ancestor

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cell clone

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A visible clone of cells

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colony

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The union of two bacterial cells during which chromosomal material is transferred from the donor to the recipient cell

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conjugation

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A bacterial cell transduced simultaneously by two donor alleles. Their frequency is used as a measure of closeness of the donor genes on the chromosome map

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cotransductant

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Bacterial cell used in studies of unidirectional DNA transmission to other cells; examples are Hfr in conjugation and phage source in transduction

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donor

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Infection of a bacterium with two genetically different phages

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double (mixed) infection

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Simultaneous transformation by two different donor markers

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double transformation

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A partly diploid E. coli cell formed from a complete chromosome (the endogenote) plus a fragment (the exogenote)

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endogenote (merozygote)

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A female bacterial cell that has just been in conjugation with a male and contains a fragment of male DNA

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exoconjugant

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A partly diploid E. coli cell formed from a complete chromosome (the endogenote) plus a fragment (the exogenote)

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exogenote

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A bacterial episome whose presence confers donor ability (maleness)

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F' plasmid

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In E. coli, a cell having a free fertility factor; a male cell

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F<+> (donor)

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In E. coli, a cell having no fertility factor; a female cell

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F<-> (recipient)

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A bacterial episome whose presence confers donor ability (maleness)

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fertility factor (F)

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The ability of certain phages to transduce any gene in the bacterial chromosome

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generalized transduction

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A piece of DNA, containing a detectable polymorphism, that is closely linked to and therefore almost always inherited with a disease-causing gene

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genetic marker

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High frequency of recombination (Hfr) cell. In E. coli, a cell having its fertility factor integrated into the bacterial chromosome; a donor (male) cell

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Hfr (high frequency of recombination)

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A technique for use with bacteria to rapidly zero in on a mutation's position on a known physical map. Random insertion of "foreign" DNA fragments inactivate any gene in which they land. When a gene of interest is inactivated, it can be located by finding the known sequence of the inserted sequence (usually a transposon)

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insertional mutagenesis

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A technique used to map bacterial genes by determining the sequence in which donor genes enter recipient cells

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interrupted mating

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The population of phage progeny breaking out of a lysed cell is known as the phage lysate

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lysate

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The rupture and death of a bacterial cell on the release of phage progeny

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lysis

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A bacterial cell capable of spontaneous lysis due, for example, to the uncoupling of a prophage from the bacterial chromosome

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lysogenic bacterium

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A partly diploid E. coli cell formed from a complete chromosome (the endogenote) plus a fragment (the exogenote)

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merozygote

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Medium containing only inorganic salts, a carbon source, and water

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minimal medium

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The infection of a bacterial culture with two different phage genotypes

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mixed (double) infection

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Origin of replication. The point of a specific sequence at which DNA replication is initiated

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origin (O)

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A virus that infects bacteria

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phage (bacteriophage)

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The production of recombinant phage genotypes as a result of doubly infecting a bacterial cell with different "parental" phage genotypes

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phage recombination

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A clear area on a bacterial lawn, left by lysis of the bacteria through progressive infections by a phage and its descendants

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plaque

Front 199

An autonomously replicating extrachromosomal DNA molecule

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plasmid

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Spreading the cells of a microorganism (bacteria, fungi) on a dish of nutritive medium to allow each cell to form a visible colony.

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plating

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An organism composed of a prokaryotic cell, such as a bacterium or a blue-green alga

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prokaryote

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A phage "chromosome" inserted as part of the linear structure of the DNA chromosome of a bacterium

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prophage

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A strain of organisms that will proliferate on minimal medium (compare auxotroph)

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prototroph

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A plasmid containing one or several transposons that bear resistance genes

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R plasmid (R Factor)

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The bacterial cell that receives DNA in a unilateral transfer between cells; examples are F<-> in a conjugation or the transduced cell in a phage-mediated transduction

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recipient

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A mutant that can grow in a normally toxic environment

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resistant mutant

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A mode of replication used by some circular DNA molecules in bacteria (such as plasmids) in which the circle seems to rotate as it reels out one continuous leading strand

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rolling circle replication

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A mutagenesis prcedure in which essentially all mutagenized progeny are recovered and are individually evaluated for mutant phenotype; often the desired phenotype is marked in some way to enable its detection

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screen

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A mutational selection technique that enriches the frequency of specific (usually rare) genotypes by establishing environmental conditions that prevent the growth or survival of other genotypes

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selective system

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The situation in which a particular phage will transduce only specific regions of the bacterial chromosome

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specialized transduction

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A phage that can become a prophage

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temperate phage

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The end represented by the last added monomer in the unidirectional synthesis of a polymer such as RNA or a polypeptide

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terminus

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The movement of genes from a bacterial donor to a bacterial recipient with a phage as the vector

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transduction

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The directed modification of a genome by the external application of DNA from a cell of different genotype

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transformation

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In a bacterial recombination experiment, an allele scored in progeny for the frequency of its consegregation with a linked selected allele

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unselected marker

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A phage that cannot become a prophage; infection by such a phage always leads to lysis of the host cell

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virulent phage

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The sudden release of a lysogenic phage from an Hfr chromosome when the prophage enters the F<-> cell followed by the subsequent lysis of the recipient cell

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zygotic induction

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The set of known alleles for a gene

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allelic series

Front 219

A situation in which a hetereozygote shows the phenotypic effects of both alleles equally

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codominance

Front 220

A test for determining whether two mutations are in different genes (they complement) or the same gene (they do not complement)

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complementation test

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A mutant allele that in single dose (a heterozygote) wipes out gene function by a spoiler effect on the protein

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dominant negative mutation

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Genotypes with mutant alleles of two different genes

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double mutants

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One gene masking expression of another

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epistasis

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The degree to which a particular genotype is expressed in the phenotype

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expressivity

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Describes an allele that expresses itself the same in a single copy (heterozygote) as in a double copy (homozygote)

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full (complete) dominance

Front 226

An RNA type that plays a role without being translated

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functional RNA

Front 227

A culture of cells composed of two different nuclear types in a common cytoplasm

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heterokaryon

Front 228

A heterozygote intermediate in phenotype between either homozygote

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incomplete dominance

Front 229

An allele that causes early death

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lethal allele

Front 230

A modifier mutation at a second locus changes the degree of expression of a mutated gene at the first locus.

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modifier

Front 231

The set of forms of one gene, differing in their DNA sequence or expression or both

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multiple alleles

Front 232

The set of forms of one gene, differing in their DNA sequence or expression or both

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multiple alleles (allelic series)

Front 233

The existence of several known alleles of a gene

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multiple allelism

Front 234

A mutation that results in complete absence of function for the gene

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null mutation

Front 235

A mid-twentieth-century hypothesis that originally proposed that each gene (nucleotide sequence) encodes a polypeptide sequence; generally true, with the exception of untranslated functional RNA

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one-gene-one-polypeptide hypothesis

Front 236

The proportion of individuals with a specific genotype that manifest that genotype at the phenotype level

Back 236

penetrance

Front 237

The temperature at which a temperature-sensitive mutant allele is expressed the same as the wild-type allele

Back 237

permissive temperature

Front 238

An allele that affects several properties of an organism

Back 238

pleiotropic allele

Front 239

The temperature at which a temperature-sensitive mutation expresses the mutant phenotype

Back 239

restrictive temperature

Front 240

An allele with wild-type function arising by the mutation of a mutant allele; caused either by a complete reversal of the original event or by a compensatory second-site mutation

Back 240

revertant

Front 241

A secondary mutation that can cancel the effect of a primary mutation, resulting in wild-type phenotype

Back 241

suppressor

Front 242

Refers to a boudle mutant that is lethal, whereas the component single mutations are not

Back 242

synthetic lethal

Front 243

A conditional mutation that procudes the mutant phenotype in one temperature

Back 243

temperature-sensitive (ts) mutations

Front 244

A protein associated with DNA polymerase III of E. coli that is not part of the catalytic core

Back 244

accessory protein

Front 245

The head-to-tail arrangement of the two entwined chains of the DNA double helix.

Back 245

antiparallel orientation

Front 246

An accessory protein whose function is to keep pol III attached to the DNA strand it is processing

Back 246

beta clamp

Front 247

Refers to specific pairing between adenine and thymine and beetween guanine and cytosine

Back 247

complementary base

Front 248

A disproved model of DNA synthesis suggesting that one-half of the daughter DNA molecules shoud have both strands composed of newly polymerized nucleotides

Back 248

conservative replication

Front 249

One of the two products of DNA replication composed of one template strand and one newly synthesized strand

Back 249

daughter molecule

Front 250

The 5-carbon sugar in a DNA nucleotide.

Back 250

deoxyribose

Front 251

A disproved model of DNA synthesis suggesting more or less random interspersion of parental and new segments in daughter DNA molecules

Back 251

dispersive replication

Front 252

In replication, an enzyme that can add only 10 nucleotides before falling off the template. Pol III, with a beta clamp, transforms from this type of enzyme into a processive enzyme that adds tens of thousands of nucleotides

Back 252

distributive enzyme

Front 253

An enzyme that joins the 3' end of the gap-filling DNA to the 5' end of the downstream Okazaki fragment

Back 253

DNA ligase

Front 254

The structure of DNA first proposed by James Watson and Francis Crick, with two interlocking helices joined by hydrogen bonds between paired bases

Back 254

double helix

Front 255

The correspondence between specific DNA base sequences and the amino acids they specify

Back 255

genetic code

Front 256

A type of enzyme that unwinds and holds apart strands of relicating DNA

Back 256

helicase

Front 257

One of several forms of an atoms having the same atomic number but differing atomic masses

Back 257

lagging strand

Front 258

In DNA replication, the strand that is made in the 5' to 3' direction by continuous polymerization at the 3' growing tip

Back 258

leading strand

Front 259

The larger of the two grooves in the DNA double helix

Back 259

major groove

Front 260

The smaller of the two grooves in the DNA double helix

Back 260

minor groove

Front 261

The nitrogen base (a purine or pyrimidine group) that forms part of a nucleotide

Back 261

nucleotide base

Front 262

A small segment of single-stranded DNA synthesized as part of the lagging strand in DNA replication

Back 262

Okazaki fragment

Front 263

An ion formed of four oxygen atoms attached to a phosphorus atom or the chemical group formed by the attachment of a phosphate ion to another chemical species by an ester bond

Back 263

phosphate

Front 264

The catalytic core of DNA pol III is part of this (p__________ III h________), a much larger complex consisting of two catalytic cores and many accessory proteins

Back 264

polymerase III (pol III) holoenzyme

Front 265

The enzyme that builds a short RNA primer at the start of a replicated DNA segment

Back 265

primase

Front 266

An RNA or DNA oligonucleotide that can serve as a template for DNA synthesis by DNA polymerase when annealed to a longer DNA molecule

Back 266

primer

Front 267

A protein complex at the replication fork whose central component is primase

Back 267

primosome

Front 268

As used here, describes the behavior of DNA polymerase III, which can perform thousands of rounds of catalysis without dissociating from its substrate (the template DNA strand)

Back 268

processive enzyme

Front 269

Part of the replisome, PCNA is the eukaryotic version of the prokaryotic sliding clamp protein

Back 269

proliferating cell nuclear antigen (PCNA)

Front 270

A type of organic molecule with a two-ring structure, including the nitrogenous bases adenine and guanine

Back 270

purine

Front 271

A type of organic molecule with a single-ring structure, including the nitrogenous bases cytosine, thymine, and uracil

Back 271

pyrimidine

Front 272

Locally opened portion of a replicating DNA double helix

Back 272

replication fork

Front 273

The molecular machine at the replication fork that coordinates the numerous reactions necessary for the rapid and accurate replication of DNA

Back 273

replisome

Front 274

The synthesis of new DNA in which half of each double helix comes from a preexisting double helix

Back 274

semiconservative replication

Front 275

A protein that binds to DNA single strands and prevents the duplex from re-forming before replication

Back 275

single-strand-binding (SSB) protein

Front 276

An enzyme, including a sequence of RNA, that adds DNA to chromosome tips

Back 276

telomerase

Front 277

The tip, or end, of a chromosome

Back 277

telomere

Front 278

A molecular "mold" that shapes the structure or sequence of another molecule; for example, the nucleotide sequence of DNA acts as a template to control

Back 278

template

Front 279

An intermediate structure in the replication of a circular bacterial chromosome

Back 279

theta structure

Front 280

An enzyme that can cut and re-form polynucleotide backbones in DNA to allow it to assume a more relaxed configuration

Back 280

topoisomerase

Front 281

The region of the RNA transcript at the 3' end downstream of the ite of translation termination

Back 281

3' untranslated region (3' UTR)

Front 282

The region of the RNA transcript at the 5' end upstream of the translation start site

Back 282

5' untranslated region (5' UTR)

Front 283

A process by which different mRNAs are produced from the same primary transcript, through variations in the splicing pattern of the transcript. Multiple mRNA "isoforms" can be produced in a single cell or the different isoforms can display different tissue-specific patterns of expression. If the alternative exons fall within the open reading frames of the mRNA isoforms, different proteins will be produced by the alternative mRNAs

Back 283

alternative splicing

Front 284

An RNA strand having a sequence complementary to a transcribed RNA strand

Back 284

antisense RNA strand

Front 285

A special structure, consisting of a 7-methylguanosine residue linked to the transcript by three phosphate groups, that is added in the nucleus to the 5' end of eukaryotic mRNA. The cap protects an mRNA from degradation and is required for translation of the mRNA in the cytoplasm

Back 285

cap

Front 286

The protein tail of the beta subunit of RNA polymerase II; it coordinates the processing of eukaryotic pre-mRNAs including capping, splicing, and termination

Back 286

carboxyl tail domain (CTD)

Front 287

The nontemplate strand of a DNA molecule having the same sequence as that in the RNA transcript

Back 287

coding strand

Front 288

Phenomenon in which both a transgene and a normal copy fail to produce a protein product

Back 288

cosuppression

Front 289

The simultaneous transcription and processing of eukaryotic pre-mRNA

Back 289

cotranscriptional processing

Front 290

A way to describe the relative location of a site in a DNA or RNA molecule. A downstream site is located closer to the 3' end of a transcription unit

Back 290

downstream

Front 291

The stage of transcription that follows initiation and precedes termination

Back 291

elongation

Front 292

A gene that is normally present in an organism, in contrast with a foreign gene from a different organism that might be introduced by transgenic techniques

Back 292

endogenous gene

Front 293

The DNA base sequences of a gene that encode amino acids. Exons are interspersed with noncoding regions called introns

Back 293

exon

Front 294

A gene that is not expressed owing to epigenetic regulation. Unlike genes that are mutant due to DNA sequence alterations, genes inactivated by silencing can be reactivated

Back 294

gene silencing

Front 295

A eukaryotic protein complex that does not take part in RNA synthesis but binds to the promoter region to attract and correctly position RNA polymerase II for transcription initiation

Back 295

general transcription factor (GTF)

Front 296

So named because the GU and AG dinucleotides are almost always at the 5' and 3' ends, respectively, of introns, where they are recognized by components of the splicosome

Back 296

GU-AG rule

Front 297

The first stage of transcription or translation. Its main function in transcription is to correctly position RNA polymerase before the elongation stage, and in translation it is to correctly position the first aminoacyl-tRNA in the P site

Back 297

initiation

Front 298

A class of functional RNA that regulates the amount of protein produced by a eukaryotic gene

Back 298

microRNA (miRNA)

Front 299

A string of adenine nucleotides added to mRNA after transcription

Back 299

poly(A) tail

Front 300

Modifications of amino acid side groups after a protein has been released from the ribosome

Back 300

posttranscriptional processing

Front 301

A very large eukaryotic protein complex comprising RNA polymerase II and the six general transcription factors (GTFs), each of which is a multiprotein complex

Back 301

preinitiation complex (PIC)

Front 302

Eukaryotic RNA before it has been processed

Back 302

primary transcript (pre-mRNA)

Front 303

A control sequence near the start of a gene

Back 303

promoter

Front 304

The complete set of protein-coding genes in a genome

Back 304

proteome

Front 305

An experiment in which cells are grown in radioactive medium for a brief period (the pulse) and then transferred to nonradioactive medium for a longer period (the chase)

Back 305

pulse-chase experiment

Front 306

A 5-carbon sugar in RNA

Back 306

ribose

Front 307

RNA that, with proteins, comprises ribosomes

Back 307

ribosomal RNA (rRNA)

Front 308

RNA component of an RNA-protein complex that has enzymatic function

Back 308

ribozyme

Front 309

A way of assessing the function of a gene by introducing special transgenic constructs to inactivate its mRNA

Back 309

RNA interference (RNAi)

Front 310

An enzyme that adds RNA nucleotides to a growing RNA chain

Back 310

RNA polymerase (RNAP)

Front 311

The bacterial multisubunit complex composed of the four subunits of the core enzyme plus the sigma factor

Back 311

RNA polymerase holoenzyme

Front 312

The collective term for the modifications to eukaryotic RNA, including capping and splicing, that are necessary before the RNA can be transported into the cytoplasm for translation

Back 312

RNA processing

Front 313

A reaction found largely in eukaryotes that removes introns and joins together exons in RNA

Back 313

RNA splicing

Front 314

The name of a popular theory that RNA must have been the genetic material in the first cells because only RNA is known to both encode genetic information and catalyze biological reactions

Back 314

RNA world

Front 315

The mechanism of RNA interference, by which the presence of double-stranded RNAs leads to the formation of short interfering RNA (siRNA) which guides the RISC complex to cleave complementary mRNAs

Back 315

RNAi pathway

Front 316

The first example of catalytic RNA; in this case, an intron that can be removed from a transcript without the aid of a protein enzyme

Back 316

self-splicing intron

Front 317

A bacterial protein that, as part of the RNA polymerase holoenzyme, recognizes the -10 and -35 regions of bacterial promoters, thus positioning the holoenzyme to initiate transcription correctly at the start site. The sigma factor dissociates from the holoenzyme before RNA synthesis

Back 317

sigma factor

Front 318

Short double-stranded RNAs produced by the cleavage of long double-stranded RNAs by Dicer

Back 318

small interfering RNA (siRNA)

Front 319

Any of several short RNAs found in the eukaryotic nucleus, where they assist in RNA processing events

Back 319

small nuclear RNA (snRNA)

Front 320

The ribonucleoprotein processing complex that removes introns from eukaryotic mRNAs

Back 320

spliceosome

Front 321

A reaction that removes introns and joins together exons in RNA

Back 321

splicing

Front 322

A DNA sequence found in many eukaryotic genes that is located about 30 bp upstream of the transcription start site

Back 322

TATA box

Front 323

A general transcription factor that bins to the TATA box and assists in attracting other general transcription factors and RNA polymerase II to eukaryotic promoters

Back 323

TATA-binding protein (TBP)

Front 324

The last stage of transcription; it results in the release of the RNA and RNA polymerase from the DNA template

Back 324

termination

Front 325

The site at which the double helix is unwound so that RNA polymerase can use one of the DNA strands as a template for RNA synthesis

Back 325

transcription bubble

Front 326

A gene that has been modified by externally applied recombinant DNA techniques and reintroduced into the genome by germ-line transformation

Back 326

transgene

Front 327

Refers to the presence of a foreign gene in a transgenic organism that does not produce an mRNA or protein product owing to epigenetic modifications

Back 327

transgene silencing

Front 328

refers to a DNA or RNA sequence located on the 5' side of a point of reference

Back 328

upstream

Front 329

A pyrimidine base in RNA in place of the thymine found in DNA

Back 329

uracil (U)

Front 330

Part of a ribosome that holds the incomping amino acid in a growing peptide chain.

Back 330

A site

Front 331

The part of a protein that must be maintained in a specific shape if the protein is to be functional - for example, in an enzyme, the part to which the substrate binds

Back 331

active site

Front 332

A small organic molecule that is a protein building block. Contiguous triplets of DNA nucleotide bases encode the 20 types of amino acids that polymerize to form biological proteins.

Back 332

amino acid

Front 333

The end of a protein having a free amino group. A protein is synthesized from the amino end at the 5' end of an mRNA to the carboxyl end near the 3' end of the mRNA during translation

Back 333

amino end

Front 334

An enzyme that attaches an amino acid to a tRNA before its use in translation. There are 20 different aminoacyl-tRNAs, one for each amino acid

Back 334

aminoacyl-tRNA synthetase

Front 335

The end of a protein having a free carboxyl group. The carboxyl end is encoded by the 3' end of the mRNA and is the last part of the protein to be synthesized in translation

Back 335

carboxyl end

Front 336

A transfer RNA molecule with an amino acid attached to its 3' end. Also called aminoacyl-tRNA

Back 336

charged tRNA

Front 337

A continuous triplet of mRNA that specifies a particular amino acid.

Back 337

codon

Front 338

The correspondence between the location of a mutant site within a gene and the location of an amino acid substitution within the polypeptide translated from that gene

Back 338

colinearity

Front 339

The region in the small ribosomal subsunit where the decision is made whether an aminoacyl-tRNA can bind in the A site. This decision is based on complementarity between the anticodon of the tRNA and the codon of the mRNA

Back 339

decoding center

Front 340

A genetic code in which some amino acids may be encoded by more than one codon each

Back 340

degenerate code

Front 341

A region of a protein associated with a particular function. Some proteins contain more than one domain

Back 341

domain

Front 342

The site on the ribosome where the deacylated tRNA can be found

Back 342

E site (aka exit site)

Front 343

A protein with a linear shape such as the components of hair and muscle

Back 343

fibrous protein

Front 344

A protein with a compact structure, such as an enzyme or an antibody

Back 344

globular protein

Front 345

A protein required for the correct initiation of translation

Back 345

initiation factor

Front 346

A special tRNA that inserts the first amino acid of a polypeptide chain into the ribosomal P site at the start of translation. The amino acid carried by the initiator in bacteria is N-formylmethionine

Back 346

initiator

Front 347

The entire set of molecular interactions within cells, including in particular protein-protein, protein-RNA, and protein-DNA interactions

Back 347

interactome

Front 348

The various types of tRNA molecules that carry a specific amino acid

Back 348

isoaccepting tRNA

Front 349

Related by different proteins. They can be generated by alternative splicing of a gene

Back 349

isoform

Front 350

Part of a protein required for its trnsport from the cytoplasm to the nucleus

Back 350

nuclear localization sequence (NLS)

Front 351

Part of a ribosome that holds a growing amino acid chain

Back 351

P site

Front 352

The site in the large ribosomal subunit at which the joining of two amino acids is catalyzed

Back 352

peptidyltransferase center

Front 353

A chain of linked amino acids; a protein

Back 353

polypeptide

Front 354

The amino acid sequence of a protein

Back 354

primary structure

Front 355

A protein that has more than one polypeptide subunit

Back 355

quaternary structure

Front 356

A protein that binds to the A site of the ribosome when a stop codon is in the mRNA

Back 356

release factor (RF)

Front 357

Folds in a polypeptide caused by attractions between amino acids close together in the primary structure

Back 357

secondary structure

Front 358

A short sequence in bacterial RNA that precedes the initiation AUG codon and serves to correctly position this codon in the P site of the ribosome by pairing (through base complementarity) with the 3' end of the 16S RNA in the 30S ribosomal subunit

Back 358

Shine-Dalgarno sequence

Front 359

The amino-terminal sequence of a secreted protein; it is required for the transport of the protein through the cell membrane

Back 359

signal sequence

Front 360

The use of basic information about cellular processes and machinery to develop drugs

Back 360

structure-based drug design

Front 361

As used here, a single polypeptide in a protein containing multiple polypeptides

Back 361

subunit

Front 362

Folds in a polypeptide caused by interactions between amino acids and water. This draws together amino acids that are far apart in the primary structure

Back 362

tertiary structure

Front 363

Three nucleotide pairs that compose a codon

Back 363

triplet

Front 364

A protein that, when attached as a multicopy chain to another protein, targets that protein for degradation by a protease called the 26S ptoeasome. The addition of single ubiquitin residues to a protein can change protein-protein interactions, as in the case of PCNA and bypass polymerases

Back 364

ubiquitin

Front 365

The process of adding ubiquitin chains to a protein targeted for degradation

Back 365

ubiquitinization

Front 366

The ability of certain bases at the third position of an anticodon in tRNA to form hydrogen bonds in various ways, causing alignment with several different possible codons

Back 366

wobble

Front 367

A protein that, when bound to a cis-acting regulatory DNA element such as an opeerator or an enhancer, activates transcription from an adjacent promoter

Back 367

activator

Front 368

A small molecule that binds to an allosteric site

Back 368

allosteric effector

Front 369

A site on a protein to which a small molecule binds, causing a change in the conformation of the protein that modifies the activity of its active site

Back 369

allosteric site

Front 370

A change from one conformation of a protein to another

Back 370

allosteric transition

Front 371

A protein that promotes the continuation of transcription by preventing the termination of transcription at specific sites on DNA

Back 371

antiterminator

Front 372

A regulatory mechanism in which the level of transcription of an operon (such as trp) is reduced when the end product of a pathway (e.g., tryptophan) is plentiful; the regulated step is after the initiation of transcription

Back 372

attenuation

Front 373

A region of RNA sequence that forms alternative secondary structures that govern the level of transcription of attenuated operons

Back 373

attenuator

Front 374

A protein that unites with cAMP at low glucose concentrations and binds to the lac promoter to facilitate RNA polymerase action

Back 374

catabolite activator protein (CAP)

Front 375

The inactivation of an operon caused by the presence of large amounts of the metabolic end product of the operon

Back 375

catabolite repression

Front 376

A site on a DNA (or RNA) molecule that functions as a binding site for a sequence-specific DNA- (or RNA-) binding protein. The term cis-acting indicates that protein binding to this site affects only nearby DNA (or RNA) sequences on the same molecule

Back 376

cis-acting element

Front 377

Mutations that cause the lac operon structural genes to be expressed regardless of whether the inducer is present

Back 377

constitutive mutation

Front 378

Genes whose products are simultaneously activated or repressed in parallel

Back 378

coordinately controlled genes

Front 379

A molecule containing a diester bond between the 3' and 5' carbon atoms of the ribose part of the nucleotide. This modified nucleotide cannot be incorporated into DNA or RNA. It plays a key role as an intracellular signal in the regulation of various processes

Back 379

cyclic adenosine monophosphate (cAMP)

Front 380

The site on a DNA-binding protein that directly interacts with specific DNA sequences

Back 380

DNA-binding domain

Front 381

A segment of regularoty DNA and the regularoty protein(s) that binds to it that govern the transcriptional state of a gene or set of genes

Back 381

genetic switch

Front 382

An environmental agent that triggers transcription from an operon

Back 382

inducer

Front 383

(1) The relief of repression of a gene or set of genes under negative control. (2) An interction between two or more cells or tissues that is required for one of those cells or tissues to change its developmental fate

Back 383

induction

Front 384

The sequence at the 5' end of an mRNA that is not translated into protein

Back 384

leader sequence

Front 385

One of the two pathways the life cycle of bacteriophage lambda, a so-called temperate phage, may take. One is the lytic cycle, in which the phage replicates and eventually lyses the cell. The alternative case, the l________ c____ is the case in which most of the phage's genes are inactive

Back 385

lysogenic cycle

Front 386

The bacteriophage life cycle that leads to lysis of the host cell

Back 386

lytic cycle

Front 387

Regulation mediated by factors that block or turn off trnscription

Back 387

negative control

Front 388

A DNA region at one end of an operon that acts as the binding site for a repressor protein

Back 388

operator

Front 389

A set of adjacent structural genes whose mRNA is synthesized in one piece, plus the adjacent regulatory signals that affect transcription of the structural genes

Back 389

operon

Front 390

A partly diploid E. coli cell formed from a complete chromosome (the endogenote) plus a fragment (the exogenote)

Back 390

partial diploid

Front 391

Regulation mediated by a protein that is required for the activation of a transcription unit

Back 391

positive control

Front 392

The expression of distinct sigma factors allows for the coordinated transcription of different sets of genes (or r_______) by a single RNA polymerase

Back 392

regulon

Front 393

A protein that binds to a cis-acting element such as an operator or a silencer, thereby preventing transcription from an adjacent promoter

Back 393

repressor

Front 394

A diffusible regulatory molecule (almost always a protein) that binds to a specific cis-acting element

Back 394

trans-acting factor

Front 395

A part of a transcription factor required for the activation of target-gene transcription; it may bind to components of the transcriptional machinery or may recruit proteins that modify chromatin structure or both

Back 395

activation domain

Front 396

A dark-staining, inactivated X chromosome in a cell.

Back 396

Barr body

Front 397

A DNA element that prevents the spread of heterochromatin by serving as a binding site for proteins that maintain euchromatic chromatin modifications such as histone acetylation

Back 397

barrier insulator

Front 398

Changes in nucleosome position along DNA

Back 398

chromatin remodeling

Front 399

A special class of eukaryotic regulatory complex that serves as a bridge to bring together regulatory proteins and RNA polymerase II

Back 399

coactivator

Front 400

Chromosomal regions of permanently condensed chromatin usually around the telomeres and centromeres

Back 400

constitutive heterochromatin

Front 401

A protein or protein complex that acts in concert with a repressor protein to repress transcription, often by modifying chromatin structure; usually not a DNA-binding entity itself

Back 401

corepressor

Front 402

D__ m__________ usually results from the enzymatic addition of methyl groups to the carbon-5 position of a specific cytosine residue

Back 402

DNA methylation

Front 403

The process in organisms using a chromosomal sex-determination mechanism (such as XX versus XY) that allows standard structural genes on the sex chromosome to be expressed at the same levels in femailes and males, regardless of the number of sex chromosomes. In mammals, dosage compensation operates by maintaining only a single active X chromosome in each cell; in Drosophila, it operates by hyperactivating the male X chromosome

Back 403

dosage compensation

Front 404

The macromolecular assembly responsible for interaction between enhancer elements and the promoter regions of genes

Back 404

enhanceosome

Front 405

A cis-acting regulatory sequence that can elevate levels of transcription from an adjacent promoter. Many tissue-specific enhancers can determine spatial patterns of gene expression in higher eukaryotes. Enhancers can act on promoters over many tens of kilobases of DNA and can be 5' or 3' of the promoters that they regulate

Back 405

enhancer element

Front 406

Regulatory elements positioned between a promoter and an enhancer. Their presence prevents the promoter from being activated by the enhancer

Back 406

enhancer-blocking insulator

Front 407

Heritable modifications in gene function not due to changes in the base sequence of the DNA of the organism. Examples of epigenetic inhereitance are paramutation, X-chromosome inactivation, and parental imprinting

Back 407

epigenetic inheritance

Front 408

A heritable alteration, such as DNA methylation or a histone modification, that leaves the DNA sequence unchanged

Back 408

epigenetic mark

Front 409

The reversible inactivation of a gene due to chromatin structure

Back 409

epigenetically silenced

Front 410

A gene that is not expressed owing to epigenetic regulation. Unlike genes that are mutant due to DNA sequence alterations, genes inactivated by silencing can be reactivated

Back 410

gene silencing

Front 411

A process in which the phenotype differs depending upon which parent transmits a particular allele

Back 411

genomic imprinting

Front 412

DNA sequence with one methylated strand and one unmethylated strand

Back 412

hemimethylated DNA

Front 413

A protein necessary for the maintenance of heterochromatin

Back 413

heterochromatin protein-1 (HP-1)

Front 414

Refers to the pattern of modification (e.g., acetylation, methylation, phosphorylation) of the histone tails that may carry information required for correct chromating assembly

Back 414

histone code

Front 415

The enzymatic activity that removes an acetyl group from a histone tail, which promotes the repression of gene transcription

Back 415

histone deacetylase (HDAT)

Front 416

The end of a histone protein protruding from the core nucleosome and subjected to posttranslational modification

Back 416

histone tail

Front 417

An overabundance of acetyl grops attached to certain amino acids of the hisone tails. Transcriptionally active chromatin is usually hyperacetylated

Back 417

hyperacetylation

Front 418

An underabundance of acetyl groups on certain amino acids of the histone tails. Transcriptionally inactive chromatin is usually hypoacetylated

Back 418

hypoacetylation

Front 419

The expression of a gene only when inherited from the father, because the copy of the gene inherited from the mother is inactive due to methylation in the course of gamete formation

Back 419

maternal imprinting

Front 420

A protein complex that acts as an adaptor that interacts with transcription factors bound to regulatory sites and with general initiation factors for RNA polymerase II-mediated transcription

Back 420

Mediator complex

Front 421

The consequence of parental imprinting is that imprinted genes are expressed as if there were only one copy of the gene present in the cell even though there are two, hence imprinting is an example of m__________ i__________

Back 421

monoallelic inheritance

Front 422

The expression of a gene only when inherited from the mother, because the allele of the gene inherited from the father is inactive due to methylation in the course of gamete formation

Back 422

paternal imprinting

Front 423

A molecule that promotes mating behavior

Back 423

pheromone

Front 424

Variegation caused by the inactivation of a gene in some cells through its abnormal juxtaposition with heterochromatin

Back 424

position-effect variegation (PEV)

Front 425

The series of transcription-factor binding sites located near the core promoter

Back 425

promoter-proximal element

Front 426

A gene whose phenotypic expression is easy to monitor; used to study tissue-specific promoter and enhancer activities in transgenes

Back 426

reporter gene

Front 427

A feature of eukaryotic regulatory proteins for which the transcriptional activation mediated by the interction of several proteins is greater then the sum of the effects of the proteins taken individually

Back 427

synergistic effect

Front 428

A DNA sequence of yeast located 5' of the gene promoter; a transcription factor binds to the UAS to positively regulate gene expression

Back 428

upstream activation sequence (UAS)

Front 429

In Drosophila, a class of cardinal genes that are activated in the zygote in response to the anterior-posterior gradients of positional information

Back 429

gap gene

Front 430

A group of adjacent functionally and structurally related genes that typically arise by gene duplication in the course of evolution

Back 430

gene complex

Front 431

A 60-base sequence of DNA found in many species' genes that controls body formation

Back 431

homeobox

Front 432

A highly conserved family of sequences, 60 amino acids in length and found within a large number of transcription factors, that can form helix-turn-helix structures and bind DNA in a sequence-specific manner

Back 432

homeodomain

Front 433

An informal term for a gene whose product is required in all cells and carries out a basic physiological function

Back 433

housekeeping gene

Front 434

Members of this gene class are the clustered homeobox-containing, homeotic genes that govern the identity of body parts along the anterior-posterior axis of most bilateral animals

Back 434

Hox gene

Front 435

A gene that produces an effect only when present in the mother

Back 435

maternal-effect gene

Front 436

In Drosophila, a member of a class of zygotically expressed genes that act at an intermediary stage in the process of establishing the correct numb ers of body segments. Pair-rule mutations have half the normal number of segments, owing to the loss of every other segment

Back 436

pair-rule gene

Front 437

The process by which chemical cues that establish cell fate along a geographic axis are established in a developing embryo or tissue primordium

Back 437

positional information

Front 438

In Drosophila, a member of a class of genes that contribute to the final aspects of establishing the correct number of segments. Segment-polarity mutations cause a loss of or change in a comparable part of each of the body segments

Back 438

segment-polarity gene

Front 439

Body parts that are members of repeated series, such as digits, ribs, teeth, limbs, and segments

Back 439

serially reiterated structure

Front 440

The identification of all the functional elements of a genome

Back 440

annotation

Front 441

The use of libraries of small chemical ligands to interfere specifically with individual protein functions, thereby phenocopying the effects of mutations in the genes encoding these functions

Back 441

chemical genetics

Front 442

The most widely used technology for isolating a specific region of chromatin so that DNA and its associated proteins can be analyzed together

Back 442

ChIP (chromatin immunoprecipitation assay)

Front 443

A set of ordered overlapping clones that constitute a chromosomal region of a genome

Back 443

clone contig

Front 444

In cloning, the plasmid or phage chromosome used to carry the cloned DNA segment

Back 444

cloning vector

Front 445

The nucleotide sequence of a segment of DNA that is in agreement with most sequence reads of the same segment from different individuals

Back 445

consensus sequence

Front 446

A cDNA clone for which only the 5' or the 3' ends or both have been sequenced; used to identify transcript ends in genomic analysis

Back 446

expressed sequence tag (EST)

Front 447

Using DNA microarrays to identify which genes are active in particular cell types

Back 447

functional genomics

Front 448

A large-scale, often multilaboratory effort required to sequence a complex genome

Back 448

genome project

Front 449

A collection of bacteria that harbor pieces of an entire other genome

Back 449

genomic library

Front 450

A member of a pair of homologous chromosomes

Back 450

homolog

Front 451

A set of DNAs containing all or most genes in a genome deposited on a small glass chip

Back 451

microarray

Front 452

A gene-sized section of a sequenced piece of DNA that begins with a start codon and ends with a stop codon; it is presumed to be the coding sequence fo a gene

Back 452

open reading frame (ORF)

Front 453

Genes in different species that evolved form a common ancestral gene by speciation

Back 453

ortholog

Front 454

In whole-genome shotgun sequence assembly, the DNA sequences corresponding to both ends of a genomic DNA insert in a recombinant clone

Back 454

paired-end read

Front 455

Genes that are related by gene duplication in a genome

Back 455

paralog

Front 456

The ordered and oriented map of cloned DNA fragments on the genome

Back 456

physical map

Front 457

A pseudogene that arose by the reverse transcription of a mature mRNA and its integration into the genome

Back 457

processed pseudogene

Front 458

A gene that does not encode protein, but whose sequence very closely resembles that of a coding gene

Back 458

pseudogene

Front 459

(1) The central framework of a chromosome to which the DNA solenoid is attached as loops; composed largely of topoisomerase (2) In genome projects, an ordered set of contigs in which there may be unsequenced gaps connected by paired-end sequence reads

Back 459

scaffold

Front 460

The compilation of thousands or millions of independent DNA sequence reads into a set of contigs and scaffolds

Back 460

sequence assembly

Front 461

A group of overlapping cloned segments

Back 461

sequence contig

Front 462

(1) The central framework of a chromosome to which the DNA solenoid is attached as loops; composed largely of topoisomerase (2) In genome projects, an ordered set of contigs in which there may be unsequenced gaps connected by paired-end sequence reads

Back 462

supercontig

Front 463

The correspondence of genes located on the same chromosome in several species

Back 463

synteny

Front 464

An attempt to interpret a genome as a holistic interacting system

Back 464

systems biology

Front 465

A method for detecting protein-protein interactions, typically performed in yeast

Back 465

two-hybrid test

Front 466

A descriptive term for a transposition mechanism in which a class 2 (DNA) transposon is excised (cut) from the donor site and inserted (pasted) into a new target site

Back 466

"cut and paste"

Front 467

A short transposable element that makes up more tha 10 percent of the human genome. Alu elements are retroelements that do not encode proteins and as such are nonautonomous elements

Back 467

Alu

Front 468

A transposable element that encodes the protein(s) - for example, transposase or reverse transcriptase - necessary for its transposition and for the transposition of nonautonomous elements in the same family

Back 468

autonomous transposable element

Front 469

A transposable element that moves through an RNA intermediate. Also called an RNA element

Back 469

class 1 element (retrotransposon)

Front 470

A transposable element that moves directly from one site in the genome to another. Also called a DNA element

Back 470

class 2 element (DNA transposon)

Front 471

The product of the fusion of two circular transposable elements to form a single, larger circle in replicative transposition

Back 471

cointegrate

Front 472

A type of bacterial transposable element containing a variety of genes that reside between two nearly identical insertion sequence (IS) elements

Back 472

composite transposon

Front 473

A transposable element (retrotransposon) of Drosophila that is flanked by long terminal repeats and typically encodes a reverse transcriptase

Back 473

copia-like element

Front 474

The DNA content of a haploid genome

Back 474

C-value

Front 475

The discrepancy (or lack of correlation) between the DNA content of an organism and its biological complexity.

Back 475

C-value paradox

Front 476

A nonautonomous transposable element named by Barbara McClintock for its ability to break chromosome 9 of maize but only in the presence of another element called Activator (Ac)

Back 476

Dissociation (Ds) element

Front 477

A class 2 transposable element found in both prokaryotes and eukaryotes and so named because the DNA element participates directly in transposition

Back 477

DNA transposon

Front 478

Describes what a transposable element does when it leaves a chromosomal location. Also called transpose

Back 478

excise

Front 479

The correction of a genetic deficiency in a cell by the addition of new DNA and its insertion into the genome. Different techniques have the potential to carry out gene therapy only in somatic tissues or, alternatively, to correct the genetic deficiency in the zygote, thereby correcting the germ line as well

Back 479

gene therapy

Front 480

A syndrome of effects including stereility, mutation, chromosome breakage, and male recombination in the hybrid progeny of crosses between certain laboratory and natural isolates of Drosophila

Back 480

hybrid dysgenesis

Front 481

A mobile piece of bacterial DNA (several hundred nucleotide pairs in length) capable of inactivating a gene into which it inserts

Back 481

insertion-sequence (IS) element

Front 482

A sequence found in identical (but inverted) form -- for example, at the opposite ends of a DNA transposon

Back 482

inverted repeat (IR)

Front 483

A type of class 1 transposable element that encodes a reverse transcriptase. LINEs are also called non-LTR retrotransposons

Back 483

long interspersed element (LINE)

Front 484

A direct repeat of DNA sequence at the 5' and 3' ends of retroviruses and retrotrnsposons

Back 484

long terminal repeat (LTR)

Front 485

A type of class 1 transposable element that terminates in long terminal repeats and encodes several proteins including reverse transcriptase

Back 485

LTR-retrotransposon

Front 486

The name given to a line of Drosophila lacking P transposable elements

Back 486

M cytotype

Front 487

A DNA transposable element in Drosophila that has been used as a tool for insertional mutagenesis and for germ-line transformation

Back 487

P element

Front 488

The chromosomally inserted DNA genome of a retrovirus

Back 488

provirus

Front 489

A mechanism of transposition that generates a new insertion element integrated elsewhere in the genome while leaving the original element at its original site of insertion

Back 489

replicative transposition

Front 490

A transposable element that useds reverse transcriptase to transpose through an RNA intermediate

Back 490

retrotransposon

Front 491

An RNA virus that uses reverse transcriptase to produce DNA from viral RNA. This DNA integrates into the host's genome, where it directs reproduction of the virus

Back 491

retrovirus

Front 492

An enzyme that catalyzes the synthesis of a DNA strand from an RNA template

Back 492

reverse transcriptase

Front 493

A site in the genome where the insertion of a transposable element is unlikely to cause a mutation, thus preventing harm to the host

Back 493

safe haven

Front 494

A type of class 1 transposable element that does not encode reverse transcriptase but is thought to use the reverse transcriptase encoded by LINEs

Back 494

short insterspersed element (SINE)

Front 495

A type of bacterial transposable element containing a variety of genes that reside between short inverted repeat sequences

Back 495

simple transposon

Front 496

A feature of certain transposable elements that facilitates their insertion into regions of the genome where they are not likely to insert into a gene causing a mutation

Back 496

targeting

Front 497

A short direct-repeat DNA sequence (typically from 2 to 10 bp in length) adjacent to the ends of a transposable element that was generated during the element's integration into the host chromosome

Back 497

target-site duplication

Front 498

An enzyme encoded by transposable elements that undergo conservative transposition

Back 498

transposase

Front 499

To move from one location in the genome to another; said of a mobile genetic element

Back 499

transpose

Front 500

A process by which mobile genetic elements move from one location in the genome to another

Back 500

transposition

Front 501

A gene or DNA segment that moves to another chromosome

Back 501

transposon

Front 502

A method used to identify and isolate a host gene through the insertion of a cloned transposable element in the gene

Back 502

transposon tagging

Front 503

A yeast LTR retrotransposon; the first isolated from any organism

Back 503

Ty element

Front 504

A phenotype characterized by frequent reversion either somatically or germinally or both due to the interaction of trnsposable elements with a host gene

Back 504

unstable phenotype

Front 505

A way to test whether a chemical compound is mutagenic by exposing special mutant bacterial strains to the product formed by that compound's digestion by liver extract and then counting the number of colonies. Only new mutations, presumably produced by the compound, can produce revertants to wild type able to form colonies

Back 505

Ames test

Front 506

A form of cell death that is a normal part of growth and development.

Back 506

apoptosis

Front 507

A DNA site that has lost a purine residue

Back 507

apurinic site

Front 508

A chemical whose molecular structure mimics that of a DNA base; because of the mimicry, the analog may act as a mutagen

Back 508

base analog

Front 509

One of several excision-repair pathways. In this pathway, subtle base-pair distortions are repaired by the creation of apurinic sites followed by repair synthesis

Back 509

base-excision repair

Front 510

A DNA polymerase that can continue to replicate DNA past a site of damage that would halt replications by the normal replicative polymerase. Bypass polymerases contribute to a damage-tolerance mechanisms called translesion DNA synthesis

Back 510

bypass (tranlesion) polymerase

Front 511

A group of disorders resulting from loss of cell cycle control.

Back 511

cancer

Front 512

A genetic disorder caused by defects in the nucleotide-excision-repair system and leading to symptoms of premature aging. Individuals with Cockayne syndrome have a mutation in one of two proteins through to recognize transcription complexes that are stalled owing to DNA damage

Back 512

Cockayne syndrome

Front 513

Nucleotide-pair substitution within a protein-coding region that leads to the replacement of an amino acid by one of similar chemical properties

Back 513

conservative substitution

Front 514

The two single-stranded crossovers (a single one is called a Holliday junction) produced during homogous recombination, according to the double-strand-break model. The model proposes that these unstable structures are resolved to produce a double-stranded reciprocal crossover

Back 514

double Holliday junction

Front 515

A DNA break cleaving the sugar-phosphate backbones of both strands of the DNA double helix

Back 515

double-strand break

Front 516

A model proposed to explain the mechanism of homologous recombination. The model posits thtat two distinct pathways are responsible for the crossover or noncrossover outcomes of meiotic recombination

Back 516

early crossover decision model

Front 517

One of the rare tautomeric forms of DNA bases (the other is the imino form -- the normal form is the keto form), which may form DNA mispairs through tautomeric shifts [the changing of one tautomer into another]

Back 517

enol

Front 518

A test used in microbes to establish the random nature of mutation or to measure mutation rates

Back 518

fluctuation test

Front 519

A mutation that alters a gene's reading frame

Back 519

frameshift mutation

Front 520

A meiotic process of directed change in which one allele directs the conversion of a partner allele into its own form

Back 520

gene conversion

Front 521

A type of nucleotide-excision repair that takes place at nontranscribed sequences

Back 521

global genomic repair (GGR)

Front 522

A disorder caused by mutations in any one of several genes encoding a particular process

Back 522

heterogenous genetic disorder

Front 523

A DNA structure resembling a single-stranded crossover, produced during meiotic recombination between the nonsister chromatids of a homologous pair

Back 523

Holliday junction

Front 524

A mechanism of DNA repair that depends on the complementarity or homology of the template strand to the strand being repaired

Back 524

homology-dependent repair system

Front 525

One of the rare tautomeric forms of DNA bases (the other is the enol form -- the normal form is the keto form), which may form DNA mispairs through tautomeric shifts [the changing of one tautomer into another]

Back 525

imino

Front 526

A mutation in which one or more nucleotide pairs is added or deleted

Back 526

indel mutation

Front 527

A mutation that arises through the action of an agent that increases the rate at which mutations occur

Back 527

induced mutation

Front 528

A mutagen that can insert itself between the stacked bases at the center of the DNA double helix, causing an elevated rate of indel mutations

Back 528

intercalating agent

Front 529

A system for repairing damage to DNA that has already been replicated

Back 529

mismatch repair

Front 530

Nucleotide-pair substitution within a protein-coding region that leads to the replacement of one amino acid by another amino acid

Back 530

missense mutation

Front 531

A substance that changes a DNA base

Back 531

mutagen

Front 532

An experiment in which experimental organisms are treated with a mutagen and their progeny are examined for specific mutant phenotypes

Back 532

mutagenesis

Front 533

Nucleotide-pair sustitution within a protein-coding region that leads to the replacement of an amino acid by one having different chemical properties

Back 533

nonconservative substitution

Front 534

A mechanism used by eukaryotes to repair double-strand breaks

Back 534

nonhomologous end joining (NHEJ)

Front 535

Nucleotide-pair substitution within a protein-coding region that changes a codon for an amino acid into a termination (nonsense) codon

Back 535

nonsense mutation

Front 536

An excision-repair pathway that breaks the phosphodiester bonds on either side of a damaged base, removing that base and several on either side followed by repair replication

Back 536

nucleotide-excision repair (NER) system

Front 537

A dominant gene that promotes cell division. An oncogene normally controls the cell cycle but leads to cancer when overexpressed

Back 537

oncogene

Front 538

The protein product of an oncogene mutation

Back 538

oncoprotein

Front 539

A single base change in DNA

Back 539

point mutation

Front 540

A gene that normally controls the cell cycle. When overexpressed, it functions as anoncogene, causing cancer

Back 540

proto-oncogene

Front 541

In microbial genetics, a way of screening colonies arrayed on a master plate to see if they are mutant under other environments; a felt pad is used to transfer the colonies to new plates

Back 541

replica plating

Front 542

An error-prone process whereby a bypass polymerase replicates past DNA damage at a stalled replicating fork by inserting nonspecific bases

Back 542

SOS system

Front 543

DNA damage occurring in the absence of exposure to mutagens; due primarily to the mutagenic action of the by-products of cellular metabolism

Back 543

spontaneous lesion

Front 544

A genetic change that is a result of mispairing when the replication machinery encounters a base in its rare tautomeric form

Back 544

sponteneous mutation

Front 545

A mutation that changes one codon for an amino acid into another codon for that same amino acid. Also called silent mutation

Back 545

synonymous mutation

Front 546

An error-free mechanism for correcting double-strand breaks that occur after the replication of a chromosomal region in a dividing cell

Back 546

synthesis-dependent strand annealing

Front 547

Isomers of a molecule such as the DNA bases that differ in the positions of the atoms and bonds between atoms

Back 547

tautomer

Front 548

The spontaneous isomerization of a nitrogen base from its normal keto form to an alternative hydrogen-bonding enol (or imino) form

Back 548

tautomeric shift

Front 549

A form of nucleotide-excision repair that is activated by stalled transcription complexes and corrects DNA damage in transcribed regions of the genome

Back 549

transcription-coupled nucleotide-excision repair (TC-NER)

Front 550

A point mutation altering a purine to a purine or a pyrimidine to a pyrimidine

Back 550

transition

Front 551

A family of DNA polymerases that can continue to replicate DNA past a site of damage that would halt replication by the normal replicative polymerase. Also known as bypass polymerases

Back 551

translesion (bypass) polymerase

Front 552

A damage-tolerance mechanism in eukaryotes that uses bypass polymerases to replicate DNA past a site of damage

Back 552

translesion DNA synthesis

Front 553

A point mutation altering a purine to a pyrimidine or vice versa

Back 553

transversion

Front 554

aka Triple expansion. The expansion of a 3-bp repeat from a relatively low number of copies to a high number of copies that is responsible for a number of genetic diseases, such as fragile X syndrom and Huntington disease

Back 554

trinucleotide repeat

Front 555

A gene encoding a protein that suppresses tumor formation. The wild-type alleles of tumor-suppressor genes are thought to function as negative regulators of cell proliferation

Back 555

tumor-suppressor gene

Front 556

A disorder caused by mutations in the transcription-coupled nucleotide-excision-repair system that leads to the frequent development of skin cancers

Back 556

xeroderma pigmentosum (XP)

Front 557

A chromosome having no centromere

Back 557

acentric chromosome

Front 558

A chromosome fragment having no centromere

Back 558

acentric fragment

Front 559

In a recriprocal translocation, the passage of a translocated and a normal chromosome to each of the poles

Back 559

adjacent-1 segregation

Front 560

aka amphidiploid; a polyploid formed from the union of two separate chromosome sets and their subsequent doubling

Back 560

allopolyploid

Front 561

In a recriprocal translocation, the passage of both normal chromosomes to one pole and both translocated chromosomes to the other pole

Back 561

alternate segregation

Front 562

An allopolyploid; a polyploid formed from the union of two separate chromosome sets and their subsequent doubling

Back 562

amphidiploid

Front 563

In a dicentric chromosome, the segment between centromeres being drawn to opposite poles at nuclear division

Back 563

anaphase bridge

Front 564

A genome having a chromosome number that differs from the normal chromosome number for the species by a small number of chromosomes

Back 564

aneuploid genome

Front 565

A polyploid formed from the doubling of a single genome

Back 565

autopolyploid

Front 566

Those in which there is no net loss or gaini of genetic material

Back 566

balanced rearrangement

Front 567

A chromosome with multiple inversions, used to retain favorable allele combinations in the uninverted homolog

Back 567

balancer

Front 568

Any type of change in chromosome structure or number

Back 568

chromosome mutation

Front 569

A missing sequence of DNA or part of a chromosome.

Back 569

deletion

Front 570

The loop formed at meiosis by the pairing of a normal chromosome and a deletion-containing chromosome

Back 570

deletion loop

Front 571

The use of a set of known deletions to map new recessive mutations by pseudodominance

Back 571

deletion mapping

Front 572

In a dicentric chromosome, the segment between centromeres being drawn to opposite poles at nuclear division

Back 572

dicentric bridge

Front 573

A chromosome with two centromeres

Back 573

dicentric chromosome

Front 574

An abnormal haploid carrying two copies of one chromosome

Back 574

disomic

Front 575

An abnormal human phenotype, including mental retardation, due to a trisomy of chromosome 21; more common babies born to older mothers

Back 575

Down syndrome

Front 576

An extra copy of a gene or DNA sequence, usually caused by misaligned pairing in meiosis; a chromosome containing repeats of part of its genetic material.

Back 576

duplication

Front 577

A small dividing mass of monoploid cells, produced from a cell destined to become a pollen cell by exposing it to cold

Back 577

embryoid

Front 578

A somatic cell with the normal number of chromosomes for that species. The human euploid chromosome number is 23 pairs

Back 578

euploid (cell)

Front 579

The idea that a normal phenotype requires a 1:1 relative proportion of genes in the genome

Back 579

gene balance

Front 580

(1) Proportionality of the expression of some biological function to the number of copies of an allele present in the cell. (2) A change in phenotype caused by an abnormal number of wild-type alleles (observed in chromosomal mutations)

Back 580

gene-dosage effect

Front 581

The collection of deleterious recessive alleles in a population

Back 581

genetic load

Front 582

A cell having six chromosome sets or an organism composed of such cells

Back 582

hexaploid

Front 583

Partly homologous chromosomes, usually indicating some original ancestral homology

Back 583

homeologous chromosomes

Front 584

A duplication in which the extra copy is not adjacent to the normal one

Back 584

insertional duplication

Front 585

A deletion within a gene

Back 585

intragenic deletion

Front 586

A chromosomal mutation consisting of the removal of a chromosome segment, its rotation through 180 degrees, and its reinsertion in the same location

Back 586

inversion

Front 587

A diploid with a normal and an inverted homolog

Back 587

inversion heterozygote

Front 588

A loop formed by meiotic pairing of homologs in an inversion heterozygote

Back 588

inversion loop

Front 589

An abnormal human male phenotype due to an extra X chromosome (XXY)

Back 589

Klinefelter syndrome

Front 590

A cell having only one chromosome set (usually as an aberration) or an organism composed of such cells

Back 590

monoploid

Front 591

A cell or individual organism that is basically diploid but has only one copy of one particular chromosome type and thus has chromosome number 2n + 1

Back 591

monosome

Front 592

A deletion of several adjacent genes

Back 592

multigenic deletion

Front 593

Crossing over between short homologous units found at different chromosomal loci

Back 593

nonallelic homologous recombination (NAHR)

Front 594

The unequal partitioning of chromosomes into gamtes during meiosis

Back 594

nondisjunction

Front 595

Refers to a cell or individual organism with one chromosomal type missing, with a chromosome number such as n - 1 or 2n - 2

Back 595

nullisomic

Front 596

An inverted chromosome that does not include the centromere

Back 596

paracentric inversion

Front 597

The production of offspring by a femaile with no genetic contribution from a male

Back 597

parthenogenesis

Front 598

An individual organism with five sets of chromosomes

Back 598

pentaploid

Front 599

An inverted chromosome that includes the centromere

Back 599

pericentric inversion

Front 600

A cell with one or more extra sets of chromosomes

Back 600

polyploid (cell)

Front 601

A giant chromosome in specific tissues of some insects, produced by an endomitotic process in which the multiple DNA sets remain bound in a haploid number of chromosomes

Back 601

polytene chromosome

Front 602

The sudden appearance of a recessive phenotype in a pedigree, due to the deletion of a masking dominant gene.

Back 602

pseudodominance

Front 603

The appearance of linkage of two genes on translocated chromosomes

Back 603

pseudolinkage

Front 604

The production of abnormal chromosomes by the breakage and incorrect rejoining of chromosomal segments; examples are inversions, deletions, and translocations

Back 604

rearrangement

Front 605

S________ D__________s, which are thought to have an important role as substrates for nonallelic homologous recombination. This class of duplications are much bigger than simple sequence repeats in that the duplicated units range from 10 to 50 kilobases in length and encompass whole genes and the regions in between

Back 605

segmental duplication

Front 606

The phenotype of an organism heterozygotic for certain types of chromosome aberration; expressed as a reduced number of viable gametes and hence reduced fertility

Back 606

semisterility

Front 607

Adjacent identical chromosome segments

Back 607

tandem duplication

Front 608

A cell having four chromosome sets; an organism composed of such cells

Back 608

tetraploid

Front 609

Exchange of genetic material between nonhomologous chromosomes

Back 609

translocation

Front 610

A cell with three complete sets of chromosomes

Back 610

triploid (cell)

Front 611

Basically a diploid with an extra chromosome of one type, producing a chromosome number of the form 2n + 1

Back 611

trisomic

Front 612

Refers to the meiotic pairing arrangement of three homologs in a triploid or trisomic

Back 612

trivalent

Front 613

An abnormal human female phenotype produced by the presence of only one X chromosome (XO)

Back 613

Turner syndrome

Front 614

A rearrangement in which chromosomal material is gained or lost in one chromosome set

Back 614

unbalanced rearrangement

Front 615

A single unpaired meiotic chromosome, as is often found in trisomics and triploids

Back 615

univalent

Front 616

A measure of the commonness of an allele in a population; the proportion of all alleles of that gene in the population that are of this specific type

Back 616

allele frequency

Front 617

Selective breeding; choosing particular individuals to reproduce together, based on the perceived value of their inherited characteristics.

Back 617

artificial selection

Front 618

The relative probability of survival and reproduction for a genotype

Back 618

Darwinian fitness

Front 619

Mating between individuals within a group or subgroup, rather than at random in a population

Back 619

endogamy

Front 620

Deliberate avoidance of mating between relatives

Back 620

enforced outbreeding

Front 621

An array of genotypic or phenotypic frequencies in a population that remain constant over time

Back 621

equilibrium distribution

Front 622

An allele for which all members of the population under study are homozygous, and so no other alleles for this locus exist in the population

Back 622

fixed allele

Front 623

A type of genetic drift in human populations in which a few members leave to found a new settlement, perepeturating a subset of the alleles from the original population

Back 623

founder effect

Front 624

Fitness differences whose intensity changes with the relative frequency of genotypes in the population

Back 624

frequency-dependent fitness

Front 625

Fitness that does not depend on interactions with other members of the same species

Back 625

frequency-independent fitness

Front 626

Changes in gene frequencies that occur when small groups of individuals are separated from or leave a larger population

Back 626

genetic drift

Front 627

The proportion in a population of individual members of a particular genotype

Back 627

genotype frequency

Front 628

An idealized state in which gene frequencies in a population do not change from generation to generation

Back 628

Hardy-Weinberg equilibrium

Front 629

A measure of the genetic variation in a population; with respect to one locus, stated as the frequency of heterozygotes for that locus

Back 629

heterozygosity

Front 630

Homozygosity that results from the inheritance of two copies of one gene that was present in an ancestor

Back 630

homozygosity by descent

Front 631

Conception of offspring whose parents are blood relative

Back 631

inbreeding

Front 632

The probability of homozygosity that results because the zygote obtains copies of the same ancestral gene

Back 632

inbreeding coefficient

Front 633

Distribution of haplotype frequencies in a population such that the frequencies are the arithmetic products of the frequencies of the alleles at the different loci in the haplotype

Back 633

linkage equilibrium

Front 634

The mean of the fitness of all individual members of a population

Back 634

mean fitness

Front 635

The number of mutation events per gene copy in a population per unit of time (e.g., per cell generation)

Back 635

mutation rate

Front 636

Differential survival and reproduction of individuals with particular phenotypes in particular environments, which may alter allele frequencies in subsequent generations

Back 636

natural selection

Front 637

Preferential mating between phenotypically unlike partners

Back 637

negative assortative mating

Front 638

Preferential mating between individuals who are unrelated

Back 638

negative inbreeding

Front 639

A phenotypic relation in which the phenotypic expression of the heterozygote is greater than that of either homozygote

Back 639

overdominance

Front 640

A group of interbreeding individuals

Back 640

population

Front 641

The study of allele frequencies in different groups of individuals

Back 641

population genetics

Front 642

A situation in which like phenotypes mate more commonly than expected by chance

Back 642

positive assortative mating

Front 643

Changes in allele frequency that result because the genes appearing in offspring are not a perfectly representative sampling of the parental genes

Back 643

random genetic drift

Front 644

(1) An experimental procedure in which only a specific type of mutant can survive. (2) The production of different average numbers of offspring by different genotyhpes in a population as a result of the different phenotypic properties of those genotypes

Back 644

selection

Front 645

A nucleotide-pair difference at a given location in the genomes of two or more naturally occurring individuals

Back 645

single-nucleotide polymorphism (SNP)

Front 646

A phenotypic relation in which the phenotypic expression of the heterozygote is less than that of either homozygote

Back 646

underdominance

Front 647

The probability that a fertilized egg will survive and develop into an adult organism

Back 647

viability

Front 648

A difference in phenotype resulting from the substitution of an "a" allele for an "A" allele when averaged over all the individual members of a population

Back 648

additive effect

Front 649

Genetic variance associated with the average effects of substituting one allele for another

Back 649

additive genetic variance

Front 650

A statistical methodology that assigns the proportion of variance in a population to different causes and their interactions

Back 650

analysis of variance

Front 651

A statistical distribution having two modes

Back 651

bimodal distribution

Front 652

A sequenced gene of previously unknown function that, becaue of its chromosomal position or some other property, becomes a candidate for a particular function such as disease determination

Back 652

candidate gene

Front 653

The value of a continuous variable around which the distribution of individual values cluster

Back 653

central tendency

Front 654

The tendency of one variable to vary in proportion to another variable, either positively or negatively

Back 654

correlation

Front 655

Comparison of the actual incidence of a trait among related individuals and the expected incidence. Used to calculate heritability.

Back 655

correlation coefficient

Front 656

A statistical measure used in computing the correlation coefficient between two variables; the covariance is the mean of (x - x bar) (y - y bar) over all pairs of values for the variables x and y, where x bar is the mean of the x values and y bar is the mean of the y values

Back 656

covariance

Front 657

The variation of values of some variable in a population or sample

Back 657

dispersion

Front 658

A graph of some precise quantitative measure of a character against its frequency of occurrence

Back 658

distribution function

Front 659

Genetic variance at a single locus sttributable to the dominance of one allele over another

Back 659

dominance variance

Front 660

The variance due to environmental variation

Back 660

environmental variance

Front 661

A trait common to members of a family

Back 661

familial trait

Front 662

A breeding technique of selecting a pair on the basis of the average performance of their progeny

Back 662

family selection

Front 663

A "step curve" in which the frequencies of various arbitrarily bounded classes are graphed

Back 663

frequency histogram

Front 664

Phenotypic similarity between different groups because the groups have inherited the same genes

Back 664

genetic correlation

Front 665

The phenotypic variance associated with the average difference in phenotype among different genotypes

Back 665

genetic variance

Front 666

An estimate of the proportion of phenotypic variation ni a group due to genes

Back 666

heritability

Front 667

Broad heritability (H<2>) The proportion of total phenotypic variance at the population level that is contributed by genetic variance

Back 667

heritability in the broad sense

Front 668

Narrow heritability (h<2>). The proportion of phenotypic variance that can be attributed to additive genetic variance

Back 668

heritability in the narrow sense

Front 669

A method of plant breeding that produces large numbers of genetically identical heterozygous plants by crossing different lines that have been made homozygous by many generations of inbreeding

Back 669

hybrid-inbred method

Front 670

The straight line that passes through a cluster of points relating a variable x with a variable y such that the sum of the squared deviations of all the y values from the line is as small as possible

Back 670

least-squares regression line

Front 671

A gene at a well-known locus whose different alleles can be distinguished by some visible phenotype, useful for locating regions containing QTLs linked to the marker gene

Back 671

marker gene

Front 672

The arithmetic average

Back 672

mean

Front 673

The mean of the values of a quantitative phenotype for two specific parents

Back 673

midparent value

Front 674

The single class in a statistical distribution having the greatest frequency

Back 674

mode

Front 675

A hypothesis that explains quantitative variation by assuming the interaction of a large number of genes (polygenes), each with a small additive effect on the character

Back 675

multiple-factor hypothesis

Front 676

The patter of phenotypes produced by a given genotype under different environmental conditions

Back 676

norm of reaction

Front 677

Phenotypic similarity between groups irrespective of whether that similarity is a result of genetic similarity

Back 677

phenotypic correlation

Front 678

The study of the genetic basis of continuous variation in phenotype

Back 678

quantitative genetics

Front 679

A gene affecting the phenotypic variation in continuously varying traits such as height and weight, among others

Back 679

quantitative trait locus (QTL)

Front 680

The straight line passing through a cluster of points that relates a variable y to a variable x and minimizes the deviations of the points from the line in the y direction

Back 680

regression line of y on x

Front 681

In statistics, the correlation between two measured quantities

Back 681

relation

Front 682

The number of occurrences of some class in a population, expressed as a proportion of the total

Back 682

relative frequency

Front 683

A small group of individual members or observations meant to be representative of a larger population from which the group has been taken

Back 683

sample

Front 684

A group of genetically varying individuals that are the offspring of a hybrid population that was the result of crossing two different genetically uniform lines

Back 684

segregating line

Front 685

The difference between the mean of a population and the mean of the individual members selected to be parents of the next generation

Back 685

selection differential

Front 686

The amount of change in he average value of some phenotypic character between the parental generation and the offspring generation as a result of the selection of parents

Back 686

selection response

Front 687

The square root of the variance

Back 687

standard deviation

Front 688

The array of frequencies of different quantitative or qualitative classes in a population

Back 688

statistical distribution

Front 689

A breeding technique in which individual organisms in which quantitative expression of a phenotype is above or below a certain value (the truncation point) are selected as parents for the next generation

Back 689

truncation selection

Front 690

The extrmely large population from which a sample is taken for statistical purposes

Back 690

universe

Front 691

A measure of the variation around the central class of a distribution; the average squared deviation of the observations from their mean value

Back 691

variance

Front 692

A surface plotted in a three-dimensional graph with all possible combinations of allele frequencies for different loci plotted in the plane and with mean fitness for each combination plotted in the third dimension; aka adaptive surface

Back 692

adaptive landscape

Front 693

A surface plotted in a three-dimensional graph with all possible combinations of allele frequencies for different loci plotted in the plane and with mean fitness for each combination plotted in the third dimension; aka adaptive landscape

Back 693

adaptive surface

Front 694

Populations separated in space and that do not exchange genes

Back 694

allopatric populations

Front 695

The formation of new species from populations that are geographically isolated from one another

Back 695

allopatric speciation

Front 696

Natural selection that results in a stable intermediate equilibrium of allele frequencies

Back 696

balancing selection

Front 697

A character that is constant in development despite environmental and genetic disturbances

Back 697

canalized characters

Front 698

Selection that changes the frequency of an allele in a constant direction, either toward or away from fixation for that allele

Back 698

directional selection

Front 699

The Darwinian explanation of evolution must be able to account for two different aspects of the history of life. One is phyletic evolution. The other is d______________ that occurs among species -- the existence of many different contemporaneous species having quite differetn forms and living in different ways.

Back 699

diversification

Front 700

A brown or black pigment found throughout much of the animal kingdom

Back 700

melanin

Front 701

The occurrence of dark forms of a population or species

Back 701

melanism

Front 702

A tool for estimating the time elapsed since two species diverged from a shared ancestor, based on DNA or protein sequence differences and mutation rate

Back 702

molecular clock

Front 703

Mutational replacement of an amino acid with one having different chemical properties

Back 703

nonsynonymous substitution

Front 704

The formation of new, related species as a result of the splitting of previously existing species

Back 704

phyletic evolution

Front 705

The failure of two species to exchange genes because the zygotes formed by the mating between them are either inviable or infertile

Back 705

postzygotic isolation

Front 706

The failure of two species to exchange genes because of barriers either to mating between them or to fertilization of the gametes of one species by the gametes of the other species

Back 706

prezygotic isolation

Front 707

Natural selection that removes deleterious variants of a DNA or protein sequence, thus reducing genetic diversity

Back 707

purifying selection

Front 708

The dependency of the fitness advantage or disadvantage of a new mutation on the mutations that have been previously fixed

Back 708

sign epistasis

Front 709

A group of organisms that can exchange genes among themselves but are reproductively isolated from other such groups

Back 709

species

Front 710

A mutation that changes one codon for an amino acid into another codon for that same amino acid. Also called silent mutation

Back 710

synonymous substitution

Front 711

A diagram showing the location of continuous pieces of the genome of one species in the genome of another species

Back 711

synteny map

Front 712

A prenatal diagnostic procedure in which a physician inserts a needle into the uterus to remove a small sample of amniotic fluid, which contains fetal cells and biochemicals.

Back 712

amniocentesis

Front 713

A protein (immunoglobulin) molecule, produced by the immune system, that recognizes a particular substance (antigen) and binds to it

Back 713

antibody

Front 714

A pattern of dark spots in a developed photographic film or emulsion in the technique of autoradiography

Back 714

autoradiogram

Front 715

Bacterial artificial chromosomes; an F plasmid engineered to act as a cloning vector that can carry large inserts

Back 715

bacterial artificial chromosome (BAC)

Front 716

A collection of cDNAs that represent the mRNAs in a particular cell type and therefore define gene expression in that cell type.

Back 716

cDNA library

Front 717

A prenatal diagnosis technique that analyzes chromosomes in chorionic villus cells, which, like the fetus, descend from the fertilized ovum.

Back 717

chorionic villus sampling

Front 718

A method for the dissection of large segments of DNA, in which a cloned segment of DNA, usually eukaryotic, is used to screen recombinant DNA clones from the same genome bank for other clones containing neighboring sequences

Back 718

chromosome walk

Front 719

Codon bias refers to an organism's preference for one or more codons for a particular amino acid over another valid codon, given that some amino acids may be specified by more than one codon. To make large amounts of human insulin, human cDNA had to be chemically modified to correspond to the codon bias of E. coli.

Back 719

codon bias

Front 720

A DNA molecule that is the complement of an mRNA, copied using reverse transcriptase.

Back 720

complementary DNA (cDNA)

Front 721

A cloning vector that can replicate autonomously like a plasmid and be packaged into a phage.

Back 721

cosmid

Front 722

The most popular method of DNA sequencing. It uses dideoxynucleotide triphosphates mixed with standard nucleotide triphosphates to produce a ladder of DNA strands whose synthesis is blocked at different lengths. This method has been incorporated into automated DNA-synthesis machines. Also called Sanger sequencing after its inventor, Frederick Sanger

Back 722

dideoxy (Sanger) sequencing

Front 723

A section of DNA that has been inserted into a vector molecule, such as a plasmid or a phage chromosome, and then replicated to form many copies

Back 723

DNA clone

Front 724

A segment of DNA that reads the same in both directions, e.g. 5'GATTC3' & 3'CTTAG5'

Back 724

DNA palindrome

Front 725

The collective techniques for obtaining, amplifying, and manipulating specific DNA fragments

Back 725

DNA technology

Front 726

Any DNA to be used in cloning or in DNA-mediated transformation

Back 726

donor DNA

Front 727

The use of a clonded fragement of wild-type DNA to transform a mutant into wild type; used in identifying a clone containing one specific gene

Back 727

functional complementation (mutant rescue)

Front 728

A method of molecular separation in which DNA, RNA, or proteins are separated in a gel matrix according to molecular size, with the use of an electrical field to draw the molecules through the gel in a predetermined direction.

Back 728

gel electrophoresis

Front 729

The inactivation of a gene by either a naturally occurring mutation or through the integration of a specially engineered introduced DNA fragment. In some systems, such inactivation is random, with the use of transgenic constructs that insert at many different locations in the genome. In other systems, it can be carried out in a directed fashion.

Back 729

gene knockout

Front 730

The insertion of a genetically engineered transgene in place of a resident gene; often achieved by a double crossover

Back 730

gene replacement

Front 731

Manipulations of genetic material. A broad term encompassing several biotechnologies

Back 731

genetic engineering

Front 732

A popular term for a transgenic organism, especially applied to transgenic agricultural organisms

Back 732

genetically modified organism (GMO)

Front 733

Genetic alterations of gametes or fertilized ova, which perpeturate the change throughout the organism and transmit it to future generations

Back 733

germline gene therapy

Front 734

Single-strand pairing of a type in which sticky ends of about 5 bases in length can base-pair with a complementary sequence

Back 734

hybridization

Front 735

Functional complementation. The use of a cloned fragment of wild-type DNA to transform a mutant into wild type; used in identifying a clone containing one specific gene

Back 735

mutant rescue (functional complementation)

Front 736

A derivative of phage P1 engineered as a cloning vector for carrying large inserts.

Back 736

P1 artificial chromosome

Front 737

A technique in which a specific sequence of DNA from a gene of interst is replcated in a test tube to rapidly produce many copies

Back 737

polymerase chain reaction (PCR)

Front 738

Describes a situation in which the phenotypic influence of a gene is altered by changes in the position of the gene within the genome

Back 738

position effect

Front 739

Identifying a gene by beginning with a phenotype withini a large family and gradually narrowing down the segment of a particular chromosome that includes the causative gene

Back 739

positional cloning

Front 740

Labeled nucleic acid segment that can be used to identify specific DNA molecules bearing the complementary sequence, usually through autoradiography or fluorescence

Back 740

probe

Front 741

A novel DNA SEQUENCE FORMED BY THE COMBINATION OF TWO NONHOMOLOGOUS dna MOLECULES

Back 741

recombinant DNA

Front 742

An endonuclease that will recognize specific target nucleotide sequences in DNA and break the DNA chain at those points; a variety of these enzymes are known, and they are extensively used in genetic engineering

Back 742

restriction fragment

Front 743

DNA sequencing technology that exploits an understanding of base-pair complementarity together with a knowledge of the basic biochemistry of DNA replication. The term d______ comes from a special modified nucleotide, called a ddNTP which can block continued DNA synthesis

Back 743

Sanger (dideoxy) sequencing

Front 744

Genetic alteration of a specific somatic tissue, not transmitted to future generations

Back 744

somatic gene therapy

Front 745

A virus that causes tumors in certain plants, often used as a vector in transgenic technology

Back 745

Ti plasmid

Front 746

A general term for any genetic unit that can insert into a chromosome, excise, and reinsert elsewhere; includes insertion sequences and transposons

Back 746

tranposable element

Front 747

An individual with an engineered genetic alteration in every cell

Back 747

transgenic organism

Front 748

A cloning-vector system in Saccharomyces cerevisiae employing yeast centromere and replication sequences

Back 748

yeast artificial chromosome (YAC)