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Homework02key - You have identified two mutants that have...

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2. You have obtained two true-breeding strains of mice, each homozygous for an independently discovered recessive mutation that prevents the formation of hair on the body. The discoverer of one of the mutant strains calls his mutation naked, and the other researcher calls her strain hairless. You cross naked and hairless mice with each other and all the offspring are phenotypically wild-type. How do you explain these results? Please draw the cross (6pt) naked (n) and hairless (h) must be mutations in two different genes and hence when you cross them they complement. Cross: nnHH x NNhh NnHh (all phenotypically wild type) 3. (10pts) You are studying sex determination in C. elegans, where XX = hermaphrodites (produce both sperm and egg but phenotypically female) and X0 = males.
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Unformatted text preview: You have identified two mutants that have opposite phenotypes: The tra-1 mutant transforms XX hermaphrodites into XX males, while the her-1 mutant results in X0 hermaphrodites. To determine the relationship between these two genes, you cross a tra-1 mutant to a her-1 mutant. The F1s are phenotypically wild type. In the F2 you see 93 wild type (XX = hermaphrodite); 32 X0 hermaphrodites and 44 XX males. a. (4pts) Formulate a hypothesis to explain these results (1 sentences max!). Recessive epistasis gene interaction because of the 9:3:4 ratio in the F2. b. (6pts) Which gene is epistatic? Explain your reasoning. Because you are seeing more tra-1 mutants, the double mutants are phenotypically tra-1 indicating that tra-1 is epistatic to her-1 ....
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