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162 Cards in this Set
- Front
- Back
A
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adenine, or adenosine
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abortive transduction
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the failure of a transducing DNA segment to be incorporated into the recipient chromosome
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acentric chromosome
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a chromosome having no centromere
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acrocentric chromosome
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a chromosome having the centromere located slightly nearer one end than the other
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active site
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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
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adaptive landscape
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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
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adaptive peak
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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
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additive genetic variance
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genetic variance associated with the average effects of substituting one allele for another
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adenine
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a purine base that pairs with thymine in the DNA double helix
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adenosine
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the nucleoside containing adenine as its base
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ATP
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adenosine triphosphate
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adjacent segregation
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in a reciprocal translocation, the passage of a translocated and a normal chromosome to each of the poles
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ADP
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adenosine diphosphate
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Ala
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alanine (an amino acid)
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alkylating agent
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a chemical agent that can add alkyl groups to another molecule; many mutagens act through alkylation
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allele
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one of two or more forms that can exist at a single gene locus
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allele frequency
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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
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allosteric transition
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a change from one conformation of a protein to another
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alternate segregation
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in a reciprocal translocation, the passage of both normal chromosomes to one pole and both translocated chromosomes to the other pole
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alternation of generations
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the alternation of gametophyte and sporophyte stages in the life cycle of a plant
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amber codon
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the codon UAG, a nonsense codon
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amber suppressor
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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
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Ames test
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a widely used test to detect possible chemical carcinogens; based on mutagenicity in the bacterium Salmonella
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amino acid
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a peptide; the basic building block of proteins (or polypeptides)
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amniocentesis
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a technique for testing the genotype of an embryo or fetus in utero with minimal risk to the mother of the child
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AMP
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adenosine monophosphate
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amphidiploid
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an allopolyploid; a polyploid formed from the union of two separate chromosome sets and their subsequent doubling
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amplification
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the production of many DNA copies from one master region of DNA
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anaphase
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an intermediate stage of nuclear division during which chromosomes are pulled to the poles of the cell
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aneuploid cell
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a cell having a chromosome number that differs from the normal chromosome number for the species by a small number of chromosomes
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Å
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angstrom
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angstrom (Å)
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a unit of length equal to 10 to the negative 10th meter; many scientists now prefer to use the nanometer
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animal breeding
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the practical application of genetic analysis for development of lines of domestic animals suited to human purposes
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annealing
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spontaneous alignment of two single DNA strands to form a double helix
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antibody
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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
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anticodon
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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
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antigen
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a molecule (typically found on the surface of a cell) whose shape triggers the production of antibodies that will bind to the antigen
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antiparallel
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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
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AP sites
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apurinic or apyrimidinic sites resulting from the loss of a purine or pyrimidine residue from the DNA
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ascospore
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a sexual spore from certain fungus species in which spores are found in a sac called an ascus
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ascus
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in fungi, a sac that encloses a tetrad or an octad of ascospores
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Asn
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asparagine (an amino acid)
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Asp
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aspartate (an amino acid)
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ATP
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adenosine triphosphate
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ATP (adenosine triphosphate)
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the "energy molecule" of cells, synthesized mainly in mitochondria and chloroplasts; energy from the breakdown of ATP drives many important reactions in the cell
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attached X
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a pair of Drosophila X chromosomes joined at one end and inherited as a single unit
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attenuator
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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
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autonomous controlling element
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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
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ARS
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autonomous replication sequence
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autonomous replication sequence (ARS)
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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
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autopolyploid
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a polyploid formed from the doubling of a single genome
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autoradiography
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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
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autosome
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any chromosome that is not a sex chromosome
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auxotroph
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a strain of microorganisms that will proliferate only when the medium is supplemented with some specific substance not required by wild-type organisms
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B chromosomes
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small plant chromosomes of variable number between individuals of a species, having no known phenotypic role
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bacteriophage (phage)
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a virus that infects bacteria
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balanced polymorphism
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stable genetic polymorphism maintained by natural selection
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Balbiani ring
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a large chromosome puff
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Barr body
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a densely staining mass that represents an X chromosome inactivated by dosage compensation
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base analog
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a chemical whose molecular structure mimics that of a DNA base; because of the mimicry, the analog may act as a mutagen
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bead theory
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the disproved hypothesis that genes are arranged on the chromosome like beads on a necklace, indivisible into smaller units of mutation and recombination
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bimodal distribution
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a statistical distribution having two modes
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binary fission
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the process in which a parent cell splits into two daughter cells of approximately equal size
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biparental zygote
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a Chlamydomonas zygote that contains cpDNA from both parents; such cells generally are rare
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blastoderm
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in an insect embryo, the layer of cells that completely surrounds an internal mass of yolk
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blending inheritance
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a discredited model of inheritance suggesting that the characteristics of an individual result from the smooth blending of fluidlike influences from its parents
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branch migration
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the process by which a single "invading" DNA strand extends its partial pairing with its complementary strand as it displaces the resident strand
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bridging cross
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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
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broad heritability (H²)
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the proportion of total phenotypic variance at the population level that is contributed by genetic variance
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bud
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a daughter cell formed by mitosis in yeast
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bud
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the daughter cell that forms a new cell wall; (the other daughter cell retains the cell wall of the parent)
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buoyant density
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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
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buoyant density
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measured by density-gradient ultracentrifugation
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C
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cytosine, or cytidine
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callus
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an undifferentiated clone of plant cells
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cAMP
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cyclic adenosine monophosphate
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cyclic adenosine monophosphate (cAMP)
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a molecule that plays a key role in the regulation of various processes within the cell
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canalized character
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a character whose phenotype is kept within narrow boundaries even in the presence of disturbing environments or mutations
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cancer
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a syndrome that involves the uncontrolled and abnormal division of eukaryotic cells
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CAP
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catabolite activator protein
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catabolite activator protein (CAP)
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a protein whose presence is necessary for the activation of the lac operon
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carbon source
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a nutrient (such as sugar) that provides carbon "skeletons" needed in the organism's synthesis of organic molecules
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carcinogen
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a substance that causes cancer
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carrier
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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
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cassette model
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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)
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CAP
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catabolite activator protein
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catabolite repression
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the inactivation of an operon caused by the presence of large amounts of the metabolic end product of the operon
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cation
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a positively charged ion
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cDNA
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complementary DNA
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cell division
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the process by which two cells are formed from one
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cell lineage
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a pedigree of cells related through asexual division
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cM
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centimorgan
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central dogma
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the hypothesis that information flows only from DNA to RNA to protein; although some exceptions are now known, the rule is generally valid
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centromere
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a kinetochore; the constricted region of a nuclear chromosome to which the spindle fibers attach during division
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character
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some attribute of individuals within a species for which various heritable differences can be defined
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character difference
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alternative forms of the same attribute within a species
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chiasma (plural, chiasmata)
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a cross-shaped structure commonly observed between nonsister chromatids during meiosis; the site of crossing-over
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chi-square (X²) test
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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
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chloroplast
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a chlorophyll-containing organelle in plants that is the site of photosynthesis
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chromatid
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one of the two side-by-side replicas produced by chromosome division
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chromatid conversion
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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
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chromatid inference
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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
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chromatin
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the substance of chromosomes; now known to include DNA, chromosomal proteins, and chromosomal RNA
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chromocenter
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the point at which the polytene chromosomes appear to be attached together
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chromomere
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a small beadlike structure visible on a chromosome during prophase of meiosis and mitosis
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chromosome
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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 aberration
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any type of change in the chromosome structure or number
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chromosome loss
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failure of a chromosome to become incorporated into a daughter nucleus at cell division
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chromosome puff
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a swelling at a site along the length of a polytene chromosome; the site of active transcription
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chromosome rearrangement
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a chromosome aberration involving new juxtapositions of chromosome parts
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chromosome set
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the group of different chromosomes that carries the basic set of genetic information for a particular species
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chromosome theory of inheritance
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the unifying theory stating that inheritance patterns may be generally explained by assuming that genes are located in specific sites on chromosomes
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cis conformation
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in a heterozygote involving two mutant sites within a gene or gene cluster
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cis dominance
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the ability of a gene to affect genes next to it on the same chromosome
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cis-trans test
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a test to determine whether two mutant sites of a gene are in the same functional unit or gene
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cistron
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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)
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clone
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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"
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code dictionary
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a listing of the 64 possible codons and their translational meanings (the corresponding amino acids)
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codominance
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the situation in which a heterozygote shows the phenotypic effects of both alleles equally
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codon
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a section of DNA (three nucleotide pairs in length) that codes for a single amino acid
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coefficient of coincidence
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the ratio of the observed number of double recombinants to the expected number
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colinearity
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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
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colony
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a visible clone of cells
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compartmentalization
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the existence of boundaries within the organism beyond which a specific clone of cells will never extend during development
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complementary DNA (cDNA)
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synthetic DNA transcribed from a specific RNA through the action of the enzyme reverse transcriptase
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complementary gene action
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intergenic complementation between mutant alleles at different loci to give wild-type phenotype
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complementary RNA (cRNA)
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synthetic RNA produced by transcription from a specific DNA single-stranded template
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complementation
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the production of a wild-type phenotype when two different mutations are combined in a diploid or a heterokaryon
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conditional mutation
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a mutation that has the wild-type phenotype under certain (permissive) environmental conditions and a mutant phenotype under other (restrictive)conditions
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conjugation
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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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conservative replication
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a disproved model of DNA synthesis suggesting that one-half of the daughter DNA molecules should have both strands composed of newly polymerized nucleotides
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constant region
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a region of an antibody molecule that is nearly identical with the corresponding regions of antibodies of different specificities
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constitutive heterochromatin
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specific regions of heterochromatin always present and in both homologs of a chromosome
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controlling element
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a mobile genetic element capable of producing an unstable mutant target gene; two types exist, the regulator and the receptor elements
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copy-choice model
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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
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correction
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the production (possibly by excision and repair) of a properly paired nucleotide pair from a sequence of hybrid DNA that contains an illegitimate pair
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correlation coefficient
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a statistical measure of the extent to which variations in one variable are related to variations in another
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cosegregation
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in Chlamydomonas, parallel behavior of different chloroplast markers in a cross, due to their close linkage on cpDNA
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cotransduction
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the simultaneous transduction of two bacterial marker genes
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cotransformation
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the simultaneous transformation of two bacterial marker genes
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coupling conformation
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linked heterozygous gene pairs in the arrangement A B/ a b
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covariance
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a statistical measure used in computing the correlation coefficient between two variables
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cpDNA
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chloroplast DNA
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cri-du-chat syndrome
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an abnormal human condition caused by deletion of part of one homolog of chromosome 5
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crisscross inheritance
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transmission of a gene from male parent to female child to male grandchild -- for example, X-linked inheritance
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cross
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the deliberate mating of two parental types of organisms in genetic analysis
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crossing-over
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the exchange of corresponding chromosome parts between homologs by breakage and reunion
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crossover suppressor
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an inversion (usually complex) that makes pairing and crossing-over impossible
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cruciform configuration
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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
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CSAR
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cytoplasmic segregation and recombination
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cytoplasmic segregation and recombination (CSAR)
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an acronym used to describe the process whereby organelle-based genes assort and recombine in a cytohet
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culture
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tissue or cells multiplying by asexual division, grown for experimentation
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Cys
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cysteine (an amino acid)
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cytidine
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the nucleoside containing cytosine as its base
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cytochromes
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a class of proteins, found in mitochondrial membranes, whose main function is oxidative phosphorylation of ADP to form ATP
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cytogenetics
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the cytological approach to genetics, mainly involving microscopic studies of chromosomes
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cytohet
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a cell containing two genetically distinct types of a specific organelle
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cytoplasm
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the material between the nuclear and cell membranes
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cytoplasm
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includes fluid (cytosol), organelles, and various membranes
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cytoplasmic inheritance
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inheritance via genes found in cytoplasmic organelles
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cytosine
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a pyrimidine base that pairs with guanine
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cytosol
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the fluid portion of the cytoplasm (outside the organelles)
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