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62 Cards in this Set
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The phenomenon in which the products of a meiotic division in an Aa heterozygous genotype are in some ratio other than the expected 1A : 1a -- for example, 3A:1a, 1A:3a, 5A:3a, or 3A:5a.
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gene conversion
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An enzyme that catalyzes the breakage and rejoining of two DNA strands in a Holliday junction to generate two independent duplex molecules.
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holliday junction- resolving enzyme
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The proportion of gametes carrying combinations of alleles that are not present in either parental chromosome.
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frequency of recombination
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In meiosis, the effect that crossing-over between one pair of nonsister chromatids may have on the probability that a second crossing-over in the same chromosome will involve the same or different chromatids; chromatid interference does not generally occur.
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chromatid interference
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The region of the chromosome that is associated with spindle fibers and that participates in normal chromosome movement during mitosis and meiosis.
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centromere
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The arrangement of linked genes in a double heterozygote in which both mutations are present in the same chromosome -- fox example, a1a2/+ +; also called coupling.
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cis configuration
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The tendency for crossing-over to inhibit the formation of another crossover nearby.
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interference
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An ascus containing two pairs of nonrecombinant spores.
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parental ditype (PD)
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A nuclease that recognizes a short nucleotide sequence (restriction site) in a DNA molecule and cleaves the molecule at that site; also called a restriction endonuclease.
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restriction enzyme
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A diagram of the order of genes in a chromosome in which the distance between adjacent genes is proportional to the rate of recombination between them; also called a genetic map.
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linkage map
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The arrangement of linked genes in a double heterozygote in which both mutations are present in the same chromosome -- fox example, a1a2/+ +; also called cis-configuration, or cis-heterozygote.
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coupling configuration
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Cross in which three genes are segregating; used to obtain unambiguous evidence of gene order.
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three point crossing
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In fungi, the genetic analysis of spores collected at random rather than from individual tetrads.
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random spore analysis
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The arrangement in linked inheritance in which a genotype heterozygous for two mutant sites has received one of the mutant sites from each parent -- that is, a1+ / +a2.
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repulsion configuration
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A diagram of the order of genes in a chromosome in which the distance between adjacent genes is proportional to the rate of recombination between them; also called a genetic map.
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genetic map
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The set of genes present together in a chromosome.
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linkage group
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Separation of a pair of alleles into different nuclei in the first meiotic division; happens when there is no crossing-over between the gene and the centromere in a particular cell.
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first division segregation
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sac containing the spores (ascospores) produced by meiosis in certain groups of fungi, including Neurospora and yeast.
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ascus
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An ascus containing spores of four different genotypes -- one each of the four genotypes possible with two alleles of each of two genes.
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tetratype
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A site in the DNA occupied by a different nucleotide pair among a significant fration of the individuals in a population.
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single- nucleotide polymorphism (SNP)
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The spores produced by meiosis in certain groups of fungi; contained in the ascus
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ascopore
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The presence in a population of two or more relatively common forms of a gene, chromosome, or genetically determined trait.
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polymorphism
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All or part of a double-stranded nucleic acid molecule in which the two strands have different hereditary origins; produced either as an intermediate in recombination or by the in vitro annealing of single-stranded complementary molecules.
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heteroduplex
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Any pair of alleles whose inheritance can be traced through a mating or through a pedigree.
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genetic marker
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A chromosome that results from crossing-over and that carries a combination of alleles differing from that of either chromosome participating in the crossover; the cell or organism that contains a recombinant chromosome.
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recombinant
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The arrangement of linked genes in a double heterozygote in which both mutations are present in the same chromosome -- fox example, a1a2/+ +; also called coupling.
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cis- heterzygote
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Segregation of a pair of alleles into different nuclei in the second meiotic division, the result of crossing-over between the gene and the centromere of the pair of homologous chromosomes.
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second division segregation
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The site or position of a particular gene on a chromosome.
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locus
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Genetic variation in a population associated with the size of restriction fragments that contain sequences homologous to a particular probe DNA; the polymorphism results from the positions of restriction sites flanking the probe, and each variant is essentially a different allele.
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restriction fragment length polymorphism (RFLP)
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An experimental value obtained by dividing the observed number of double recombinants by the expected number calculated under the assumption that the two events take place independently.
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coefficient of coincidence
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The genetic distance between two marker genes expressed as the sum of the length in map units across of a set of small, nonoverlapping intervals between the marker genes; corresponds to one-half of the average number of chiasmata between the genes multiplied by 100.
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map distance
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The cytological manifestation of crossing-over; the cross-shaped exchange configuration between nonsister chromatids of homologous chromosomes that is visible in prophase I of meiosis. The plural can be either chiasmata or (chiasmas.
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chiasma
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An ascus containing two pairs of recombinant spores.
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nonparental ditype (NPD)
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Any mechanism that arrests the cell cycle until one or more essential processes are completed.
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checkpoint
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A cross-shaped configuration of two DNA duplexes formed as an intermediate in recombination.
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holliday junction
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Exchange of parts between DNA molecules or chromosomes; recombination in eukaryotes usually entails a reciprocal exchange of parts, but in prokaryotes it is often nonreciprocal.
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recombination
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A unit of distance in the genetic map equal to 1 percent recombination; also called a map unit.
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centimorgan
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The tendency of genes located in the same chromosome to be associated in inheritance more frequently than expected from their independent assortment in meiosis.
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linkage
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The tendency of genes located in the same chromosome to be associated in inheritance more frequently than expected from their independent assortment in meiosis.
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map unit
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The arrangement in linked inheritance in which a genotype heterozygous for two mutant sites has received one of the mutant sites from each parent -- that is, a1+ +a2.
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trans configuration
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A diagram showing the locations and relative spacing of genes along a chromosome.
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chromosome map
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Alleles present in an offspring chromosome in the same combination as that found in one of the parental chromosomes.
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parental combination
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If recombination frequency between two genes is 3 percent, what is the distance between the genes in map units on the linkage map__
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3
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On a chromosomal map, 2 map units are equal to __
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2% of recombination
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The maximum recombination frequency between two genes is___
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50%
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A coefficient of coincidence of 0.5 means that___
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The frequency of double crossovers is 0.5 of the number expected if there were no interference
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The physical exchange of segments between homologous chromosomes is called ___
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crossing over
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In the absence of recombination, what ratio of phenotypes is expected in the progeny of the cross AB/ab x aB/Ab?
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1 aaB- : 2 A-B- : 1A-bb
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In tetrad analysis 3-strand double crossing-over between two linked genes results in___
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TT tetrad
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The tendency for crossing-over to inhibit the formation of another crossover nearby is called ___
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interference
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Gene conversion results from a normal DNA repair process in the cell known as ___
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excision repair
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Genes a and b are 10.0 map units apart, and genes b and c are 20 map units apart (gene order is a ? b ? c). In the absence of interference, what is the probability of a double crossover in these regions?
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2%
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Two genes that undergo independent assortment, indicated by a recombination frequency equal to ____, either are in non-homologous chromosomes or are located far apart in a single chromosome.
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50%
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facts about gene mapping are__
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1) distance measured by probability of recombination between 2 genes (2) distance is measured by map units and centimorgans. (3) independent assortment is indicated by a recombination frequency of 50% (4) genes with recombination frequencies of less than 50% are likely on the same chromosome
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___equals 1/2 of the average number of crossovers that take place in the region per meiotic cell.
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map distance
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___ is how much recombination is actually abserved in a particular experiment
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recombination frequency
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all known genes in a chromosome are the ___
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linkage group
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crossover in one region of a chromosome reduces probability of a second crossover in a nearby region
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chromosome interference
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Bivalents that lack chiasmata to help hold them together are prone to undergo nondisjunction. true of false?
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true
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In Genetics, a Holiday junction is ___
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(1) is resolved by the Holliday junction-resolving enzyme.
(2) A structure wear pairing partners are switched in a crossover pathway |
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____demonstrate that crossing-over takes place at the four-strand stage of meiosis and is reciprical.
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tetratype tetrads
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these are true concerning polymorphic DNA sequences and genetic mapping___
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(1) some are detected by a restriction endonuclease and cleaves the double stranded DNA molecule wherever a particular short sequence of bases is present (2) different DNA fragment lengths are created based on the cleavage sites and are known as restriction fragment length polmorphisms
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