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22 Cards in this Set

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a spore contained in an ascus or that was produces inside an asucs; specific to fungi classified as ascomycetes; typically a single ascus will contain 8 ascospores; a meiotic spore
ascus (pl. asci)
the sexual spore-bearing cell (sac) produced in ascomycete fungi
centimorgan (cM)
a unit of distance between genes on chromosomes representing 1% crossing over between two genes; equivalent to 1 map unit (m.u.).(one cM corresponds to about 1 million base pairs in humans on avg)
an exchange of genetic material between homologous chromosomes by breakage and reunion; the exchange of material between nonsister chromatids during meiosis is the basis of genetic recombination (online definition: one of the final phases of genetic recombination, which occurs during prophase I of meiosis in a process called synapsis. Usually occurs when matching regions on matching chromosomes break and then reconnect to the other chromosome.)
four-strand double crossover
a single crossover between two chromatids and then a second single crossover between the remaining chromatids. the result is that all four products are recombinant.
genetic map (chromosome map)
a diagram showing the location of genes on chromosomes (includes the DNA seq of a gene with introns and exons, 3' or 5' transcribed-untranslated regions, termination signal, regulatory elements such as promoters, enhancers and it may include known mutations defining alternative alleles of the same gene)
interference (positive interference)
a measure of the degree to which one crossover affects the incidence of another crossover in an adjacent region of the same chromatid (the reduction of the likelihood of another crossover in the vicinity of a nearby crossover); negative interference increases the chance of another crossover; positive interference reduces the possibility of a second crossover event.
the tendency of certain loci or alleles to be inherited together; genetic loci that are physically close to one another on the same chromosome tend to stay together during meiosis and are thus genetically linked; occurs as an exception to independent assortment
linkage group
genes that are inherited as a single unit because they are near one another on the same chromosome. ex: in fruit flies, the genes affecting eye color and wing length are inherited together because they appear on the same chromosome
linkage map
a genetic map of a species that shows the position of its known genes or genetic markers relative to each other in terms of recombination frequency, rather than as specific physical distance along each chromosome; critical for identifying the location of genes that cause genetic diseases
lod score
(logarithm (base 10) of odds) is a statistical test to determine whether two loci are linked or unlinked; positive LOD scores favor the presence of linkage, whereas negative LOD scores indicate that linkage is less likely. a LOD score of 4 indicates that linkage is 10,000 times more likely than nonlinkage. by convention, scores of 3-4 are signs of linkage
**map distance
look up in book
mapping function
a mathematical formula that relates map distances to recombination frequencies
non-parental ditypes (NPD)
a spore arrangement in that contains only the two recombinant-type ascospores (assuming two segregating loci). [a tetrad type containing two diff genotypes, both of which are recombinant]
parental ditype
a tetrad type containing 2 diff genotypes, both of which are parental. A spore arrangement in Ascomycetes that contains only the two-recombinant-type ascospores
noncrossover gamete
a gamete whose chromosomes have undergone no genetic recombination
recombinant frequency (% recombinants)
a measure of genetic linkage and is used in the creation of a genetic linkage map; the frequency with which a single chromosomal crossover will take place bw two genes during meiosis; a centimorgan (cM) is a unit that describes a recombination frequency of 1%
crossover gamete
a gamete whose chromosomes have undergone genetic recombination
syntenic genes
book definition: in somatic cell genetics, a method for determining whether two genes are on the same chromosome
(internet definition: co-localization of genetic loci on the same chromosome within an individual or species; related to genetic linkage: linkage bw two loci is established by the observation of lower-than-expected recombination frequencies between them. in contrast, any loci on the same chromosome are by definition syntenic, even if their recombination frequency cannot be distinguished rom unlinked loci by practical experiments. Thus, in theory, all linked loci are syntenic, but not all syntenic loci are necessarily linked.)
the 4 chromatids that make up paired homologs in the prophase of the first meiotic division. In eukaryotes with a predominant haploid stage (some algae and fungi) tetrad denotes the 4 haploid cels produced by a single meiotic division.
three-strand double crossover
results when one chromatid crosses over with two other chromatids. The result is two parental and two recombinant progeny, the same as a single crossover event.
two-strand double crossover
result of two chiasma between the two loci involving the same two sister chromatids. these two events cancel each other out and result in parental or non-recombinatnt progeny