Homework02 BIS101-003/Engebrecht 10/02/08 Suggested problems and homework for week #2 Problems suggested for the whole class these are not to be turned in, but are for practice/study aid. The following problems can be done after the meiosis lecture: 8th edition: Ch. 3: 5, 10, 19, 25, 40 9th edition: Ch.2: 9, 14, 16 Ch. 3: 2, 46 The following problems are on gene interactions: Ch. 6 (both 8th and 9th edition): 10, 12, 16, 28, 31, 33, 35, 36, 39 101D assignment #2 (due beginning 10/9/08) is listed on the next page.
1. (6pts) Consider a diploid yeast strain with the genotype HIS1/his1 ADE2/ade2. Capital letters (HIS1 and ADE2) indicate wild-type genes, whereas lowercase letters (his1 and ade2) denote mutant alleles. HIS1 is located on chromosome V, a small chromosome while ADE2 maps to chromosome XV, a large chromosome. Drawn are chromosomes in Anaphase I (top) and Anaphase II (bottom). The longer chromosome represents XV, the shorter chromosome represents V. Complete the figure by 1) adding the correct allele designations on each sister chromatid and 2) use arrows to indicate the direction of chromosome movement. Be sure to give both possible anaphase configurations (left and right). Assume that there is no crossing between over the gene and the centromere.
Anaphase I
Anaphase II
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)
3. (10pts) You are studying sex determination in C. elegans, where XX = hermaphrodites (produce both sperm and egg but phenotypically female) and X0 = males. You have identified two mutants that have opposite phenotypes: The tra-1 mutant transforms 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 wild type. In the F2 you see 93 wild type (XX = hermaphrodite): 32 X0 hermaphrodites: 44 XX males. a. (4pts) Formulate a hypothesis to explain these results (1 sentences max!).
b. (6pts) Which gene is epistatic? Explain your reasoning (1 sentences max!).