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174 Cards in this Set

  • Front
  • Back
macromolecule
a large polymer such as DNA, a protein, or a polysaccharide
map unit (m.u.)
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
mapping function
a formula expressing the relationship between distance in a linkage map and recombinant frequency
marker retention
a technique used in yeast to test the degree of linkage between two mitochondrial mutations
maternal effect
the environmental influence of the mother's tissues on the phenotype of the offspring
maternal inheritance
a type of uniparental inheritance in which all progeny have the genotype and phenotype of the parent acting as the female
mating types
the equivalent in lower organisms of the sexes in higher organisms; the mating types typically differ only physiologically and not in physical form
matroclinous inheritance
inheritance in which all offspring have the nucleus-determined phenotype of the mother
mean
the arithmetic average
medium
any material on (or in) which experimental cultures are grown
meiocyte
cell in which meiosis occurs
meiosis
two successive nuclear divisions (with corresponding cell divisions) that produce gametes (in animals) or sexual spores (in plants and fungi) having one-half of the genetic material of the original cell
meiospore
cell that is one of the products of meiosis in plants
melting
denaturation of DNA
Mendelian ratio
a ratio of progeny phenotypes reflecting the operation of Mendel's laws
Mendel's first law
the two members of a gene pair segregate from each other during meiosis; each gamete has an equal probability of obtaining either member of the gene pair
Mendel's second law
the law of independent assortment; unlinked or distantly linked segregating gene pairs assort independently at meiosis
merozygote
a partially diploid E. coli cell formed from a complete chromosome (the endogenote) plus a fragment (the exogenote)
mRNA
messenger RNA
Met
methionine (an amino acid)
metabolism
the chemical reactions that occur in a living cell
metacentric chromosome
a chromosome having its centromere in the middle
metaphase
an intermediate stage of nuclear division when chromosomes align along the equatorial plane of the cell
midparent value
the mean of the values of a quantitative phenotype for two specific parents
minimal medium
a medium containing only inorganic salts, a carbon source, and water
missense mutation
a mutation that alters a codon so that it encodes a different amino acid
mitochondrion
a eukaryotic organelle that is the site of ATP synthesis and of the citric acid cycle
mitosis
a type of nuclear division (occurring at cell division) that produces two daughter nuclei identical to the parent nucleus
mitotic crossover
a crossover resulting from the pairing of homologs in a mitotic diploid
mode
the single class in a statistical distribution having the greatest frequency
modifier gene
a gene that affects the phenotypic expression of another gene
molecular genetics
the study of the molecular processes underlying gene structure and function
monocistronic mRNA
an mRNA that codes for one protein
monoecious plant
a plant species in which male and female organs are found on the same plant but in different flowers (for example, corn)
monohybrid cross
a cross between two individuals identically heterozygous at one gene pair -- for example, Aa X Aa
monoploid
a cell having only one chromosome set (usually an aberration), or an organism composed of such cells
monosomic
a cell or individual that is basically diploid but that has only one copy of one particular chromosome type and thus has chromosome number 2n - 1
mosaic
a chimera; a tissue containing two or more genetically distinct cell types, or an individual composed of such tissues
messenger RNA (mRNA)
an RNA molecule transcribed from the DNA of a gene, and from which a protein is translated by the action of ribosomes
mtDNA
mitochondrial DNA
mu phage
a kind ("species") of phage with properties similar to those of insertion sequences, being able to insert, transpose, inactivate, and cause rearrangements
multimeric structure
a structure composed of several identical or different subunits held together by weak bonds
multiple allelism
the existence of several known alleles of a gene
multiple-factor hypothesis
a hypothesis to explain quantitative variation by assuming the interaction of a large number of genes (polygenes), each with a small additive effect on the character
multiplicity of infection
the average number of phage particles that infect a single bacterial cell in a specific experiment
mutagen
an agent that is capable of increasing the mutation rate
mutant
an organism or cell carrying a mutation
mutant allele
an allele differing from the allele found in the standard, or wild-type
mutant hunt
the process of accumulating different mutants showing abnormalities in a certain structure or function, as a preparation for mutational dissection of that function
mutant site
the damaged or altered area within a mutated gene
mutation
the process that produces a gene or a chromosome set differing from the wild-type; the gene or chromosome set that results from such a process
mutation breeding
use of mutagens to develop variants that can increase agricultural yield
mutation breeding
use of mutagens to develop variants that can increase agricultural yield
mutation event
the actual occurrence of a mutation in time and space
mutation frequency
the frequency of mutants in a population
mutation rate
the number of mutation events per gene per unit of time (for example, per cell generation)
mutational dissection
the study of the components of a biological function through a study of mutations affecting that function
muton
the smallest part of a gene that can be involved in a mutation event; now known to be a nucleotide pair
myeloma
a cancer of the bone marrow
negative assortative mating
preferential mating between phenotypically unlike partners
negative control
regulation mediated by factors that block or turn off transcription
Neurospora
a pink mold commonly found growing on old food
neutral mutation
a mutation that has no effect on the Darwinian fitness of its carriers; a mutation that has no phenotype effect
neutral petite
a petite that produces all wild-type progeny when crossed with wild-type
nicking
nuclease action to sever the sugar-phosphate backbone in one DNA strand at one specific site
nitrocellulose filter
a type of filter used to hold DNA for hybridization
nitrogen bases
types of molecules that form important parts of nucleic acids, composed of nitrogen-containing ring structures; hydrogen bonds between bases link the two strands of a DNA double helix
nondisjunction
the failure of homologs (at meiosis) or sister chromatids (at mitosis) to separate properly to opposite poles
nonlinear tetrad
a tetrad in which the meiotic products are in no particular order
non-Mendelian ratio
an unusual ration of progeny phenotypes that does not reflect the simple operation of Mendel's laws; for example, mutant: wild ratios of 3:5, 5:3, 6:2, or 2:6 in tetrads indicate that gene conversion has occurred
NPD
nonparental ditype
nonparental ditype (NPD)
a tetrad type containing two different genotypes, both of which are recombinant
nonsense codon
a codon for which no normal tRNA molecule exists; the presence of a nonsense codon causes termination of translation (the end of the polypeptide chain)
the three nonsense codons
amber, ocher, opal
nonsense mutation
a mutation that alters a gene so as to produce a nonsense codon
nonsense suppressor
a mutation that produces an altered tRNA that will insert an amino acid during translation in response to a nonsense codon
norm of reaction
the pattern of phenotypes produced by a given genotype under different environmental conditions
nuclease
an enzyme that can degrade DNA by breaking its phosphodiester bonds
nucleoid
a DNA mass within a chloroplast or mitochondrion
nucleolar organizer
a region or regions of the chromosome set physically associated with the nucleolus and containing rRNA genes
nucleolus
an organelle found in the nucleus, containing rRNA and amplified multiple copies of the genes coding for RNA
nucleoside
a nitrogen base bound to a sugar molecule
nucleosome
a nu body; the basic unit of eukaryotic chromosome structure; a ball of eight histone molecules wrapped about by two coils of DNA
nucleotide
a molecule composed of a nitrogen base, a sugar, and a phosphate group; the basic building block of nucleic acids
nucleotide pair
a pair of nucleotides (one in each strand of DNA) that are joined by hydrogen bonds
nucleotide-pair substitution
the replacement of a specific nucleotide pair by a different pair; often mutagenic
null allele
an allele whose effect is either an absence of normal gene product at the molecular level or an absence of normal function at the phenotypic level
nullisomic
a cell or individual with one chromosomal type missing, with a chromosome number such as n - 1 or
2n - 2
ocher codon
the codon UAA, a nonsense codon
octad
an ascus containing eight ascospores, produced in species in which the tetrad normally undergoes a post-meiotic mitotic division
oncogene
a gene that causes cancer
opal codon
the codon UGA, a nonsense codon
open reading frame
a nucleotide sequence with no stop codons, discovered by sequencing
operator
a DNA region at one end of an operon that acts as the binding site for repressor protein
operon
a set of adjacent structural genes whose mRNA is synthesized in one piece, plus the adjacent regulatory signals that affect transcription on the structural genes
ORF
open reading frame
open reading frame (ORF)
generally synonymous with URF
organelle
a subcellular structure having a specialized function -- for example, the mitochondrion, the chloroplast, or the spindle apparatus
origin of replication
the point of specific sequence at which DNA replication is initiated
overdominance
a phenotypic relation in which the phenotypic expression of the heterozygote is greater than that of either homozygote
palindrome
a sequence of DNA that is the same when each strand is read in the same direction
paracentric inversion
an inversion not involving the centromere
parental ditype (PD)
a tetrad type containing two different genotypes, both of which are parental
particulate inheritance
the model proposing that genetic information is transmitted from one generation to the next in discrete units ("particles"), so that the character of the offspring is not a smooth blend of essences from the parents
pathogen
an organism that causes disease in another organism
patroclinous inheritance
inheritance in which all offspring have the nucleus-based phenotype of the father
pedigree
a "family tree" drawn with standard genetic symbols, showing inheritance patterns for specific phenotypic characters
peptide bond
a bond joining two amino acids
penetrance
the proportion of individuals with a specific genotype who manifest that genotype at the phenotype level
pericentric inversion
an inversion that involves the centromere
permissive conditions
those environmental conditions under which a conditional mutant shows the wild-type phenotype
petite
a yeast mutation producing small colonies and altered mitochondrial functions
cytoplasmic petites
neural and suppressive petites; the mutation is a deletion in mitochondrial DNA
segregational petites
the mutation occurs in nuclear DNA
Phe
phenylalanine (an amino acid)
phenocopy
an environmentally induced phenotype that resembles the phenotype produced by a mutation
phenotype
the form taken by some character or group of characters in a specific individual; the detectable outward manifestations of a specific genotype
phenotypic sex determination
sex determination by nongenetic means
Philadelphia chromosome
a translocation between the long arms of chromosomes 9 and 22, often found in the white blood cells of patients with chronic myeloid leukemia
phosphodiester bond
a bond between a sugar group and a phosphate group
phosphodiester bonds
form the sugar-phosphate backbone of DNA
pilus (plural, pili)
a conjugation tube; a hollow hairlike appendage of a donor E. coli cell that acts as a bridge for transmission of donor DNA to the recipient cell during conjugation
plant breeding
the application of genetic analysis to development of plant lines better suited for human purposes
plaque
a clear area on a bacterial lawn, left by lysis of the bacteria through progressive infections by a phage and its descendants
plasmid
autonomously replicating extrachromosomal DNA molecule
plate
a flat dish used to culture microbes; to spread cells over the surface of solid medium in a flat dish
pleiotropic mutation
a mutation that has effects on several different characters
point mutation
a mutation that can be mapped to one specific locus
Poisson distribution
a mathematical expression giving the probability of observing various numbers of a particular event in a sample when the probability of an event on any one trial is very small, but on which large numbers of trials have been made
poky
a slow-growing mitochondrial mutant in Neurospora
polar gene conversion
a gradient of conversion frequency along the length of a gene
polar granules
granules at the anterior end of the cytoplasm of a Drosophila egg
polar mutation
a mutation that affects the transcription or translation of the part of the gene or operon only on one side of the mutant site -- for example, nonsense mutations, frame-shift mutations, and IS-induced mutations
poly-A tail
a string of adenine nucleotides added to mRNA after transcription
polyacrilamide
a material used to make electrophoretic gels for separation of mixtures of macromolecules
polycistronic mRNA
an mRNA that codes for more than one protein
polymorphism
the occurrence in a population (or among populations) of several phenotypic forms associated with alleles of one gene or homologs of one chromosome
polypeptide
a chain of linked amino acids; a protein
polyploid
a cell having three or more chromosome sets, or an organism composed of such cells
polysaccharide
a biological polymer composed of sugar subunits--for example, starch or cellulose
polytene chromosome
a giant chromosome produced by an endomitotic process in which multiple DNA sets remain bound in a haploid number of chromosomes
position effect
used to describe a situation where the phenotypic influence of a gene is altered by changes in the position of the gene within the genome
position-effect variegation
variegation caused by the inactivation of a gene in some cells through its abnormal juxtaposition with heterochromatin
positive assortative mating
a situation in which like phenotypes mate more commonly than expected by chance
positive control
regulation mediated by a protein that is required for the activation of a transcription unit
primary structures of a protein
the sequence of amino acids in the polypeptide chain
Pro
proline (an amino acid)
probe
defined nucleic acid segment that can be used to identify specific DNA molecules bearing the complementary sequence, usually through autoradiography
product of meiosis
one of the (usually four) cells formed by the two meiotic divisions
product rule
the probability of two independent events occurring simultaneously is the product of the individual probabilities
proflavin
a mutagen that tends to produce frame-shift mutations
prokaryote
an organism composed of a prokaryotic cell, such as bacteria and blue-green algae
prokaryotic cell
a cell having no nuclear membrane and hence no separate nucleus
promoter
a regulatory region a short distance from the 5' end of a gene that acts as the binding site for RNA polymerase
prophage
a phage "chromosome" inserted as part of the linear structure of the DNA chromosome of a bacterium
prophase
the early stage of nuclear division during which chromosomes condense and become visible
propositus
in a human pedigree, the individual who first came to the attention of the geneticist
proto-oncogene
a gene that, when mutated or otherwise affected, becomes an oncogene
protoplast
a plant cell whose wall has been removed
prototroph
a strain of organisms that will proliferate on minimal medium
provirus
a virus "chromosome" integrated into the DNA of the host cell
pseudodominance
the sudden appearance of a recessive phenotype in a pedigree, due to deletion of a masking dominant gene
pseudogene
an inactive gene derived from an ancestral active gene
pulse-chase experiment
an experiment in which cells are grown in radioactive medium for a brief period and then transferred to nonradioactive medium for a longer period
pulsed-field gel electrophoresis
an technique in which gel is subjected to electrical fields alternating between different angles, allowing very large DNA fragments to "snake" through the gel, and hence permit efficient separation of mixtures of such large fragments
Punnett square
a grid used as a graphic representation of the progeny zygotes resulting from different gamete fusions in a specific cross
pure-breeding line or strain
a group of identical individuals that always produce offspring of the same phenotype when intercrossed
purine
a type of nitrogen base
purine bases in DNA
adenine and guanine
nitrogen bases
purine and pyrimidine
purine bases in DNA
adenine and guanine
pyrimidine bases in DNA
cytosine and thymine
quantitative variation
the existence of a range of phenotypes for a specific character, differing by degree rather than by distinct qualitative differences
quaternary structure of a protein
the multimeric constitution of the protein