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78 Cards in this Set

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Meiosis
part of the process of gamete formation, consisting of chromosome conjugation and two cell divisions, in the course of which the diploid chromosome number becomes reduced to the haploid.
Interphase
the period of the cell cycle during which the nucleus is not undergoing division, typically occurring between mitotic or meiotic divisions. Also called interkinesis.
Prophase
the first stage of mitosis or meiosis in eukaryotic cell division, during which the nuclear envelope breaks down and strands of chromatin form into chromosomes.
Metaphase
the stage in mitosis or meiosis in which the duplicated chromosomes line up along the equatorial plate of the spindle.
Anaphase
the stage in mitosis or meiosis following metaphase in which the daughter chromosomes move away from each other to opposite ends of the cell.
Telophase
the final stage of meiosis or mitosis, in which the separated chromosomes reach the opposite poles of the dividing cell and the nuclei of the daughter cells form around the two sets of chromosomes.
Haploid
an organism or cell having only one complete set of chromosomes, ordinarily half the normal diploid number.
Gene
the basic physical unit of heredity; a linear sequence of nucleotides along a segment of DNA that provides the coded instructions for synthesis of RNA, which, when translated into protein, leads to the expression of hereditary character.
homologous
Having the same morphology and linear sequence of gene loci as another chromosome.
dominant gene
A gene that is expressed phenotypically in heterozygous or homozygous individuals.
recessive gene
A gene that is phenotypically expressed in the homozygous state but has its expression masked in the presence of a dominant gene.
phenotype
the appearance of an organism resulting from the interaction of the genotype and the environment.
genotype
the genetic makeup of an organism or group of organisms with reference to a single trait, set of traits, or an entire complex of traits.
homozygous
having identical pairs of genes for any given pair of hereditary characteristics.
heterozygous
having dissimilar pairs of genes for any hereditary characteristic.
locus
the chromosomal position of a gene as determined by its linear order relative to the other genes on that chromosome.
allele
any of several forms of a gene, usually arising through mutation, that are responsible for hereditary variation.
monohybrid cross
the offspring of individuals that differ with respect to a particular gene pair.
dihybrid cross
hybridization using two traits with two alleles each
test cross
A cross between an individual exhibiting the dominant phenotype of a trait and an individual that is homozygous recessive for that trait in order to determine the genotype of the dominant individual.
generations
All of the offspring that are at the same stage of descent from a common ancestor
Law of Segregation
random segregation of alleles to separate gametes
Law of Independent Assortment
chromosomes segregate separately from other nonhomologous chromosomes
Incomplete dominance
the appearance in a heterozygote of a trait that is intermediate between either of the trait's homozygous phenotypes
codominance
of or pertaining to two different alleles that are fully expressed in a heterozygous individual
multiple alleles
a series of three or more alternative or allelic forms of a gene, only two of which can exist in any normal, diploid individual.
epistasis
a form of interaction between nonallelic genes in which one combination of such genes has a dominant effect over other combinations.
pleiotropy
the phenomenon of one gene being responsible for or affecting more than one phenotypic characteristic.
polygenic inheritance
the heredity of complex characters that are determined by a large number of genes, each one usually having a relatively small effect.
linkage
an association between two or more genes on a chromosome that tends to cause the characteristics determined by these genes to be inherited as an inseparable unit.
non-disjunction
The failure of paired chromosomes or sister chromatids to separate and go to different cells during meiosis.
deletion
a type of chromosomal aberration in which a segment of the chromosome is removed or lost.
duplication
a type of chromosomal aberration in which a region of the chromosome is repeated.
translocation
a chromosomal rearrangement in which a segment of genetic material from one chromosome becomes heritably linked to another chromosome.
inversion
a type of chromosomal aberration in which the position of a segment of the chromosome is changed in such a way that the linear order of the genes is reversed.
semiconservative replication
The normal process of DNA synthesis, in which the two original strands of the molecule separate, and each acts as a template on which a new complementary strand is laid down.
DNA polymerase
Any of various enzymes that function in the replication and repair of DNA by catalyzing the linking of dATP, dCTP, dGTP, and dTTP in a specific order, using single-stranded DNA as a template.
helicase
any of various enzymes that catalyze the unwinding and separation of double-stranded DNA or RNA during its replication
replication fork
a Y-shaped part of a chromosome that is the site for DNA strand separation and then duplication
deletion
a type of chromosomal aberration in which a segment of the chromosome is removed or lost.
insertion
The addition, as by mutation, of one or more nucleotides to a chromosome.
transcription
the process by which genetic information on a strand of DNA is used to synthesize a strand of complementary RNA.
mRNA
messenger RNA.
chromatin
the readily stainable substance of a cell nucleus, consisting of DNA, RNA, and various proteins, that forms chromosomes during cell division.
nucleosome
Any of the repeating subunits of chromatin, consisting of a DNA chain coiled around a core of histones.
bacteriophages
A virus that infects and lyses certain bacteria.
capsid
the coiled or polyhedral structure, composed of proteins, that encloses the nucleic acid of a virus.
retroviruses
any of a family of single-stranded RNA viruses having a helical envelope and containing an enzyme that allows for a reversal of genetic transcription, from RNA to DNA rather than the usual DNA to RNA, the newly transcribed viral DNA being incorporated into the host cell's DNA strand for the production of new RNA retroviruses: the family includes the AIDS virus and certain oncogene-carrying viruses implicated in various cancers.
plasmids
A circular, double-stranded unit of DNA that replicates within a cell independently of the chromosomal DNA. Plasmids are most often found in bacteria and are used in recombinant DNA research to transfer genes between cells.
regulation of gene expression
operons
repressible enzyme
tryp operon, when tryptophan present binds to repressor and triggers it to bind to DNA, anabolic pathway
intron
A segment of a gene situated between exons that is removed before translation of messenger RNA and does not function in coding for protein synthesis.
exon
any portion of an interrupted gene that is represented in the RNA product and is translated into protein.
translation
the process by which a messenger RNA molecule specifies the linear sequence of amino acids on a ribosome for protein synthesis.
mRNA
messenger RNA
codon
a triplet of adjacent nucleotides in the messenger RNA chain that codes for a specific amino acid in the synthesis of a protein molecule
tRNA
transfer RNA
anticodon
a sequence of three nucleotides in a region of transfer RNA that recognizes a complementary coding triplet of nucleotides in messenger RNA during translation by the ribosomes in protein biosynthesis.
rRNA
The RNA that is a permanent structural part of a ribosome. (ribosomal RNA)
ribosome
a tiny, somewhat mitten-shaped organelle occurring in great numbers in the cell cytoplasm either freely, in small clusters, or attached to the outer surfaces of endoplasmic reticula, and functioning as the site of protein manufacture.
wobble
The ability of one tRNA anticodon to recognize two mRNA codons, as in the third base of a tRNA anticodon pairing with any of a variety of bases that occupy the third position of different mRNA codons instead of pairing according to base pairing rules.
stop codon
Any of three codons, UAA, UAG, or UGA, that signal the termination of the synthesis of a protein. Also called chain termination codon.
start codon
Either of two codons, AUG or GUG, that signal the initiation of translation and the first amino acid in a polypeptide chain. Also called chain initiation codon.
plasmid
A circular, double-stranded unit of DNA that replicates within a cell independently of the chromosomal DNA. Plasmids are most often found in bacteria and are used in recombinant DNA research to transfer genes between cells.
conjugation
a temporary union of two bacteria, in Escherichia and related groups, in which genetic material is transferred by migration of a plasmid, either solitary or as part of a chromosome, from one bacterium, the donor, to the other, the recipient; sometimes also including the transfer of resistance to antibiotics.
transduction
the transfer of genetic material from one cell to another by means of a virus.
transformation
the transfer of genetic material from one cell to another resulting in a genetic change in the recipient cell.
regulation of gene expression
operons
regulatory gene
any gene that exercises control over the expression of another gene or genes
polymerase chain reaction
A technique for amplifying DNA sequences in vitro by separating the DNA into two strands and incubating it with oligonucleotide primers and DNA polymerase. It can amplify a specific sequence of DNA by as many as one billion times and is important in biotechnology, forensics, medicine, and genetic research.
promoter
a site on a DNA molecule at which RNA polymerase binds and initiates transcription.
operator
a segment of DNA that interacts with a regulatory molecule, preventing transcription of the adjacent region.
structural gene
A gene that determines the amino acid sequence of a protein.
inducible enzyme
lac operon, when lactose present binds to repressor and induces it to release DNA, catabolic pathway
repressible enzyme
tryp operon, when tryptophan (corepressor) present binds to repressor and triggers it to bind to DNA, anabolic pathway
restriction enzymes
Chemicals used in the lab to cut up DNA at specific sites so that it may be sequenced. They function in nature as a form of bacterial self-protection that can cut up foreign DNA. The use of restriction enzymes is crucial in DNA fingerprinting.
ligase
any of a class of enzymes that catalyze the joining of two molecules by formation of a covalent bond accompanied by the hydrolysis of ATP.
transformation
the transfer of genetic material from one cell to another resulting in a genetic change in the recipient cell.