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15 Cards in this Set
- Front
- Back
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Genetic linkage
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genes can be linked to each other or reside on the same chromosome. If two genes are close together on the same chromosome pair, they do not assort independently.
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Genetic distance
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The distance between gene loci on a chromosome can be measured in terms of the recombination frequency (RF), produced by crossing over between two loci during meiosis. Roughly, 1% recombination equals 1 map unit (m.u.) for short distances (e.g., 1 to 15% RF)
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Gene order and the 3 factor cross (trihybrid cross)
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Interlocus map distances based on recombination measurements are roughly additive and can be used to determine gene order.
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Interference
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One crossover can influence the occurrence of a second crossover in an adjacent region. Interference distorts map distances.
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Mapping function
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For recombination frequencies (RF) larger than 15%, the 1 to 1 relationship between RF and m.u. breaks down. For example, an RF of 27.5% actually equals 40 m.u
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T/F?
Genes are linked to other genes. |
True
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nomenclature
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the locus is given a one- or two-letter italic designation based on the mutant or alternate allele. The recessive mutant allele is indicated with lower case letters while the normal (wild type) allele is indicated with capital letters or simply with a "+" sign.
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Recombination
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produces genotypes with new combinations of parental alleles.
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intrachromosomal recombination
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When genes are linked on the same chromosome...ratio something like 0.8 : 0.8 : 0.2 : 0:2
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Crossing over
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occurs at the “4 strand” stage of Prophase I of meiosis and involves structures called “chiasma,”
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T/F Crossing over is between chromosomes, not chromatids
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False: Crossing over is between chromatids, not chromosomes
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What regions have more crossovers?
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Longer regions have more crossovers and higher RFs
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trihybrid cross
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is performed involving three loci
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double crossove
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Only the middle of three loci is changed
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genetic map
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means of displaying the number of genes, their order along the chromosome and their relative distances from each other
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