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162 Cards in this Set

  • Front
  • Back
adenine, or adenosine
abortive transduction
the failure of a transducing DNA segment to be incorporated into the recipient chromosome
acentric chromosome
a chromosome having no centromere
acrocentric chromosome
a chromosome having the centromere located slightly nearer one end than the other
active site
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
adaptive landscape
the surface plotted in a three-dimensional graph, with all possible combinations of allele frequencies for different loci plotted in the plane, and mean fitness for each combination plotted in the third dimension
adaptive peak
a high point on an adaptive landscape; selection tends to drive the genotype composition of the population toward a combination corresponding to an adaptive peak
additive genetic variance
genetic variance associated with the average effects of substituting one allele for another
a purine base that pairs with thymine in the DNA double helix
the nucleoside containing adenine as its base
adenosine triphosphate
adjacent segregation
in a reciprocal translocation, the passage of a translocated and a normal chromosome to each of the poles
adenosine diphosphate
alanine (an amino acid)
alkylating agent
a chemical agent that can add alkyl groups to another molecule; many mutagens act through alkylation
one of two or more forms that can exist at a single gene locus
allele frequency
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
allosteric transition
a change from one conformation of a protein to another
alternate segregation
in a reciprocal translocation, the passage of both normal chromosomes to one pole and both translocated chromosomes to the other pole
alternation of generations
the alternation of gametophyte and sporophyte stages in the life cycle of a plant
amber codon
the codon UAG, a nonsense codon
amber suppressor
a mutant allele coding for tRNA whose anticodon is altered in such a way that the tRNA inserts an amino acid at an amber codon in translation
Ames test
a widely used test to detect possible chemical carcinogens; based on mutagenicity in the bacterium Salmonella
amino acid
a peptide; the basic building block of proteins (or polypeptides)
a technique for testing the genotype of an embryo or fetus in utero with minimal risk to the mother of the child
adenosine monophosphate
an allopolyploid; a polyploid formed from the union of two separate chromosome sets and their subsequent doubling
the production of many DNA copies from one master region of DNA
an intermediate stage of nuclear division during which chromosomes are pulled to the poles of the cell
aneuploid cell
a cell having a chromosome number that differs from the normal chromosome number for the species by a small number of chromosomes
angstrom (Å)
a unit of length equal to 10 to the negative 10th meter; many scientists now prefer to use the nanometer
animal breeding
the practical application of genetic analysis for development of lines of domestic animals suited to human purposes
spontaneous alignment of two single DNA strands to form a double helix
a protein (immunoglobulin) molecule produced by the immune system that recognizes a particular foreign antigen and binds to if; if the antigen is on the surface of the cell, this binding leads to cell aggregation and subsequent destruction
a nucleotide triplet in a tRNA molecule that aligns with a particular codon in mRNA under the influence of the ribosome so that the peptide carried by the tRNA is inserted in a growing protein chain
a molecule (typically found on the surface of a cell) whose shape triggers the production of antibodies that will bind to the antigen
a term used to describe the opposite orientations of the two strands of a DNA double helix; the 5' end of one strand aligns with the 3' end of the other strand
AP sites
apurinic or apyrimidinic sites resulting from the loss of a purine or pyrimidine residue from the DNA
a sexual spore from certain fungus species in which spores are found in a sac called an ascus
in fungi, a sac that encloses a tetrad or an octad of ascospores
asparagine (an amino acid)
aspartate (an amino acid)
adenosine triphosphate
ATP (adenosine triphosphate)
the "energy molecule" of cells, synthesized mainly in mitochondria and chloroplasts; energy from the breakdown of ATP drives many important reactions in the cell
attached X
a pair of Drosophila X chromosomes joined at one end and inherited as a single unit
a region adjacent to the structural genes of the trp operon; this region acts in the presence of tryptophan to reduce the rate of transcription form the structural genes
autonomous controlling element
a controlling element that apparently has both regulator and receptor functions combined in the single unit, which enters a gene and causes an unstable mutation
autonomous replication sequence
autonomous replication sequence (ARS)
a segment of a DNA molecule necessary for the initiation of its replication; generally a site recognized and bound by the proteins of the replication system
a polyploid formed from the doubling of a single genome
a process in which radioactive materials are incorporated into cell structures, which are then placed next to a film of photographic emulsion, thus forming a pattern on the film corresponding to the location of the radioactive compounds within the cell
any chromosome that is not a sex chromosome
a strain of microorganisms that will proliferate only when the medium is supplemented with some specific substance not required by wild-type organisms
B chromosomes
small plant chromosomes of variable number between individuals of a species, having no known phenotypic role
bacteriophage (phage)
a virus that infects bacteria
balanced polymorphism
stable genetic polymorphism maintained by natural selection
Balbiani ring
a large chromosome puff
Barr body
a densely staining mass that represents an X chromosome inactivated by dosage compensation
base analog
a chemical whose molecular structure mimics that of a DNA base; because of the mimicry, the analog may act as a mutagen
bead theory
the disproved hypothesis that genes are arranged on the chromosome like beads on a necklace, indivisible into smaller units of mutation and recombination
bimodal distribution
a statistical distribution having two modes
binary fission
the process in which a parent cell splits into two daughter cells of approximately equal size
biparental zygote
a Chlamydomonas zygote that contains cpDNA from both parents; such cells generally are rare
in an insect embryo, the layer of cells that completely surrounds an internal mass of yolk
blending inheritance
a discredited model of inheritance suggesting that the characteristics of an individual result from the smooth blending of fluidlike influences from its parents
branch migration
the process by which a single "invading" DNA strand extends its partial pairing with its complementary strand as it displaces the resident strand
bridging cross
a cross made to transfer alleles between two sexually isolated species by first transferring the alleles to an intermediate species that is sexually compatible with both
broad heritability (H²)
the proportion of total phenotypic variance at the population level that is contributed by genetic variance
a daughter cell formed by mitosis in yeast
the daughter cell that forms a new cell wall; (the other daughter cell retains the cell wall of the parent)
buoyant density
a measure of the tendency of a substance to float in some other substance; large molecules are distinguished by their differing buoyant densities in some standard fluid
buoyant density
measured by density-gradient ultracentrifugation
cytosine, or cytidine
an undifferentiated clone of plant cells
cyclic adenosine monophosphate
cyclic adenosine monophosphate (cAMP)
a molecule that plays a key role in the regulation of various processes within the cell
canalized character
a character whose phenotype is kept within narrow boundaries even in the presence of disturbing environments or mutations
a syndrome that involves the uncontrolled and abnormal division of eukaryotic cells
catabolite activator protein
catabolite activator protein (CAP)
a protein whose presence is necessary for the activation of the lac operon
carbon source
a nutrient (such as sugar) that provides carbon "skeletons" needed in the organism's synthesis of organic molecules
a substance that causes cancer
an individual who possesses a mutant allele but does not express it in the phenotype because of a dominant allele partner; thus, an individual of genotype Aa is a carrier of a if there is complete dominance of A over a
cassette model
a model to explain mating-type interconversion in yeast; a copy of either type of cassette may be transposed to the mating-type locus, where it is "played" (transcribed)
catabolite activator protein
catabolite repression
the inactivation of an operon caused by the presence of large amounts of the metabolic end product of the operon
a positively charged ion
complementary DNA
cell division
the process by which two cells are formed from one
cell lineage
a pedigree of cells related through asexual division
central dogma
the hypothesis that information flows only from DNA to RNA to protein; although some exceptions are now known, the rule is generally valid
a kinetochore; the constricted region of a nuclear chromosome to which the spindle fibers attach during division
some attribute of individuals within a species for which various heritable differences can be defined
character difference
alternative forms of the same attribute within a species
chiasma (plural, chiasmata)
a cross-shaped structure commonly observed between nonsister chromatids during meiosis; the site of crossing-over
chi-square (X²) test
a statistical procedure used to determine whether differences between sets of observed frequencies exceed those expected by chance if the sets were randomly selected from a single large population
a chlorophyll-containing organelle in plants that is the site of photosynthesis
one of the two side-by-side replicas produced by chromosome division
chromatid conversion
a type of gene conversion that is inferred from the existence of identical sister-spore pairs in a fungal octad that shows a non-Mendelian allele ratio
chromatid inference
a situation in which the occurrence of a crossover between any two nonsister chromatids can be shown to affect the probability of those chromatids being involved in other crossovers in the same meiosis
the substance of chromosomes; now known to include DNA, chromosomal proteins, and chromosomal RNA
the point at which the polytene chromosomes appear to be attached together
a small beadlike structure visible on a chromosome during prophase of meiosis and mitosis
a linear end-to-end arrangement of genes and other DNA, sometimes with associated protein and RNA
chromosome aberration
any type of change in the chromosome structure or number
chromosome loss
failure of a chromosome to become incorporated into a daughter nucleus at cell division
chromosome puff
a swelling at a site along the length of a polytene chromosome; the site of active transcription
chromosome rearrangement
a chromosome aberration involving new juxtapositions of chromosome parts
chromosome set
the group of different chromosomes that carries the basic set of genetic information for a particular species
chromosome theory of inheritance
the unifying theory stating that inheritance patterns may be generally explained by assuming that genes are located in specific sites on chromosomes
cis conformation
in a heterozygote involving two mutant sites within a gene or gene cluster
cis dominance
the ability of a gene to affect genes next to it on the same chromosome
cis-trans test
a test to determine whether two mutant sites of a gene are in the same functional unit or gene
originally defined as a functional genetic unit within which two mutations cannot complement. Now equated with the term gene as the region of DNA that encodes a single polypeptide (or functional RNA molecule such as tRNA or rRNA)
a group of genetically identical cells or individuals derived by asexual division from a common ancestor; (colloquial) an individual formed by some asexual process so that it is genetically identical to its "parent"
code dictionary
a listing of the 64 possible codons and their translational meanings (the corresponding amino acids)
the situation in which a heterozygote shows the phenotypic effects of both alleles equally
a section of DNA (three nucleotide pairs in length) that codes for a single amino acid
coefficient of coincidence
the ratio of the observed number of double recombinants to the expected number
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
a visible clone of cells
the existence of boundaries within the organism beyond which a specific clone of cells will never extend during development
complementary DNA (cDNA)
synthetic DNA transcribed from a specific RNA through the action of the enzyme reverse transcriptase
complementary gene action
intergenic complementation between mutant alleles at different loci to give wild-type phenotype
complementary RNA (cRNA)
synthetic RNA produced by transcription from a specific DNA single-stranded template
the production of a wild-type phenotype when two different mutations are combined in a diploid or a heterokaryon
conditional mutation
a mutation that has the wild-type phenotype under certain (permissive) environmental conditions and a mutant phenotype under other (restrictive)conditions
the union of two bacterial cells, during which chromosomal material is transferred from the donor to the recipient cell
conservative replication
a disproved model of DNA synthesis suggesting that one-half of the daughter DNA molecules should have both strands composed of newly polymerized nucleotides
constant region
a region of an antibody molecule that is nearly identical with the corresponding regions of antibodies of different specificities
constitutive heterochromatin
specific regions of heterochromatin always present and in both homologs of a chromosome
controlling element
a mobile genetic element capable of producing an unstable mutant target gene; two types exist, the regulator and the receptor elements
copy-choice model
a model of the mechanism for crossing-over, suggesting that crossing-over occurs during chromosome division and can occur only between two supposedly "new" nonsister chromatids; the experimental evidence does not support this model
the production (possibly by excision and repair) of a properly paired nucleotide pair from a sequence of hybrid DNA that contains an illegitimate pair
correlation coefficient
a statistical measure of the extent to which variations in one variable are related to variations in another
in Chlamydomonas, parallel behavior of different chloroplast markers in a cross, due to their close linkage on cpDNA
the simultaneous transduction of two bacterial marker genes
the simultaneous transformation of two bacterial marker genes
coupling conformation
linked heterozygous gene pairs in the arrangement A B/ a b
a statistical measure used in computing the correlation coefficient between two variables
chloroplast DNA
cri-du-chat syndrome
an abnormal human condition caused by deletion of part of one homolog of chromosome 5
crisscross inheritance
transmission of a gene from male parent to female child to male grandchild -- for example, X-linked inheritance
the deliberate mating of two parental types of organisms in genetic analysis
the exchange of corresponding chromosome parts between homologs by breakage and reunion
crossover suppressor
an inversion (usually complex) that makes pairing and crossing-over impossible
cruciform configuration
a region of DNA with palindromic sequences in both strands, so that each strand pairs with itself to form a helix extending sideways from the main helix
cytoplasmic segregation and recombination
cytoplasmic segregation and recombination (CSAR)
an acronym used to describe the process whereby organelle-based genes assort and recombine in a cytohet
tissue or cells multiplying by asexual division, grown for experimentation
cysteine (an amino acid)
the nucleoside containing cytosine as its base
a class of proteins, found in mitochondrial membranes, whose main function is oxidative phosphorylation of ADP to form ATP
the cytological approach to genetics, mainly involving microscopic studies of chromosomes
a cell containing two genetically distinct types of a specific organelle
the material between the nuclear and cell membranes
includes fluid (cytosol), organelles, and various membranes
cytoplasmic inheritance
inheritance via genes found in cytoplasmic organelles
a pyrimidine base that pairs with guanine
the fluid portion of the cytoplasm (outside the organelles)