Lecture7_Linkage - Percentage of recombinants is...

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Extensions to Mendel I I. Linkage and linkage mapping A. Morgan’s lab found a series of genes on the X chromosome; inheritance pattern B. Crosses with linked genes Linked genes = genes that are located on the same chromosome 1. Prediction of linkage hypothesis: linked genes should violate a. Review notation for genes on X chromosome Autosome = a non-sex chromosome b. Notation for X-linked, linked genes: c. Simulate gamete formation in a X wY / X Wy fly 2. Morgan's experimental test of the linkage prediction: pure-line white-eyed, normal-bodied female X red-eyed, yellow-bodied male Parentals: F 1 females: F 1 males:
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a. Let F 1 s mate. Predict genotypes and phenotypes, and ratios, for F 2 MALE offspring 3. What is going on? a. What are the genotypes of the “weird” males? white eyes, yellow body: red eyes, normal body: b. Crossing over as an explanation F 1 females: X wY /X Wy Recombination = generation of a new combination of alleles along a chromosome Recombination is a result of crossing over C. Sturtevant’s insight and linkage mapping
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Unformatted text preview: Percentage of recombinants is proportional to Yellow is at If cross yellow and sable body, get Sable V white eye Crossveinless wings unit of a centimorgan (cM): idea of a genetic map (aka meiotic map): II. Sources of genetic variation 1. Independent assortment of maternal and paternal chromosomes if n = , how many different gametes in terms of different combinations of maternal and paternal chromosomes? 2 n different gametes possible 2. Crossing over routinely occurs multiple times produces new combinations of 3. Outcrossing (vs. self-fertilization) Outcrossing = combine haploid genomes from different parents to form diploid offspring potentially, new combinations of alleles 4. Mutation Are mutations frequent enough to generate significant genetic variation? Based on estimates of frequency of mutation per gene and number of genes in human genome, calculate that each human gamete carries an average of mutations....
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Lecture7_Linkage - Percentage of recombinants is...

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