REINAGEL_mt2_key

REINAGEL_mt2_key - BICD100 FALL 2005 MIDTERM 2 VERSION A...

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BICD100 FALL 2005 REINAGEL MIDTERM 2 VERSION A KEY 1. You are studying three autosomal recessive mutations in Drosophila that are linked: rosy, hairy, and wobbly. You cross a fly from a pure-breeding wobbly strain to a fly from a pure-breeding hairy, rosy strain to obtain an F1. You then cross the F1 flies to flies from a pure-breeding rosy, hairy, wobbly strain to obtain the following F2: 12 rosy wobbly 84 hairy rosy wobbly 407 hairy wobbly 1941 wobbly 2031 hairy rosy 12 hairy 408 rosy 105 wild type TOTAL 5000 Derive the most accurate map you can of the order of these genes and the distances between them. State the amount of interference, if any. SHOW ALL YOUR WORK. Parents: wild type x rosy hairy wobbly wobblyrosy hairy 4.3 16.8 Interference = 0.33 (expected 35.7 double xo, observed 24)
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2. You cross an arg3 haploid yeast strain to an ind2 haploid yeast strain to obtain a diploid that is heterozygous for both genes: arg3 + x + ind2 arg3 + diploid + ind2 The yeast strain produces unordered tetrads. For each of the following situations, diagram the 4-chromatid stage of a meiosis producing a Tetratype tetrad. The diagram should show the location(s) of crossover(s) if any, and clearly indicate which chromatids segregate together in order to explain the genotypes of the 4 spores. For full credit you must show the minimum number of crossovers that could explain the tetrad type. If there is more than one way to obtain the specified tetrad type using the same number of crossover events, show only one example. a) if arg3 and ind2 are linked: In this case a TT arises from any single crossover between them, for example: ---.---arg3---IND+--to produce: arg3 IND+ ---.---arg3---IND+-- arg3 ind2 X ===.===ARG+===ind2== ARG+ IND+ ===.===ARG+===ind2== ARG+ ind2 b) if arg3 and ind2 are unlinked, and arg3 is tightly linked to its centromere. In this case a TT arises from any single crossover between ind2 and its centromere, for example: ---.---------ind2-- --.arg3---------- for ind2 arg3 ---.---------ind2-- --.arg3---------- IND+ arg3 X ===.=========IND+== ==.ARG+=========== ind2 ARG+ ===.=========IND+== ==.ARG+=========== IND+ ARG+
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3. In yeast Saccharomyces cerevisiae you cross two haploids: tyr4 val1 x phe7 . In the resulting diploid, all three genes are heterozygous. From the following unordered tetrads, determine the linkage relationships between these three loci, including any centromeres that can be determined. SHOW YOUR WORK. Tetrad genotypes number of tetrads tyr4 val1 phe+ 119 tyr4 val1 phe+ tyr+ val+ phe7 tyr+ val+ phe7 tyr4 val+ phe+ 125 tyr4 val+ phe+ tyr+ val1 phe7 tyr+ val1 phe7 tyr4 val1 phe+ 33 tyr4 val1 phe7 tyr+ val+ phe+ tyr+ val+ phe7 tyr4 val+ phe+ 27 tyr4 val+ phe7 tyr+ val1 phe+ tyr+ val1 phe7 Tetrad tyr/val tyr/phe val/phe I = 119 PD PD PD II = 125 NPD PD NPD III =33 PD TT TT IV = 27 NPD TT TT PD = NPD PD>T>NPD PD=NPD conclusion: unlinked linked unlinked & both linked to their centromeres tyr - phe = ½ TT / Total x 100 = [0.5(33 + 27)/(304)] x 100 = 9.87 cM
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REINAGEL_mt2_key - BICD100 FALL 2005 MIDTERM 2 VERSION A...

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