bioeMCB C142-fall06-mt1-Slatkin-soln

bioeMCB C142-fall06-mt1-Slatkin-soln - MCB 142/ IB 163...

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MCB 142/ IB 163 Midterm 1, 2006 Name _____________________________ Page 1 of 9 GSI_______________________________ Put your name and your GSI’s name on all 9 pages. The pages will separated for grading. No papers, notes, books, calculators, computers, telephones, mp3 players or other electronic devices may be used. You can leave your answers as fractions and sums. Write all answers in the space provided. You can use the backs of the pages for your own notes. Be sure to answer all parts of all 15 questions. The numbers in parentheses are the points for each part. The total is 150. 1. Suppose that in flies, you find an autosomal mutant pd that causes polka-dot wings; pd + is the wild-type alleles. This mutant is partially penetrant in heterozygotes: 25% have polka-dot wings. It is completely penetrant in mutant homozygotes. Assume you cross a pure-breeding line of polka-dot flies with a pure breeding line of flies with wild-type wings. a. (4) What is the fraction of flies in F 2 population with polka-dot wings? Answer: 3/8 b. (4) What is the fraction of flies with polka-dot wings in the backcross of the F 1 to the polka-dot population? Answer: 5/8 2. (8) Humans and chimpanzees had a common ancestor 6 million years ago (6x10 6 ). Suppose there are 100 4-fold redundant sites in the sequence of α -globin. If the rate of neutral substitution is 2x10 –9 per site per year, what is the expected number of differences between humans and chimpanzees would you expect to see at the 4-fold redundant sites of α -globin? Answer: D=2μTL=2(2x10 –9 ) x(6x10 6 )x10 2 =2.4.
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MCB 142/ IB 163 Midterm 1, 2006 Name _____________________________ Page 2 of 9 GSI_______________________________ 3. In the above pedigree for mice, black indicates that the individual has blue fur, white indicates that the individual has the normal agouti fur, and the diagonal lines indicate that the fur color is unknown because of an unfortunate accident in the laboratory. Assume blue fur color is determined by an allele of a single gene. a. (3) Based on the information in the pedigree, did I-2 have agouti or blue fur? Answer: Agouti b. (3) Does your answer to part a depend on whether the blue gene is X-linked? Answer: No c. (3) Suppose you could mate III-1 with a female from a pure-breeding line of agouti mice. Describe how you would determine whether the blue gene is X-linked. Answer: Interbreed the hybrid offspring. If there are any blue females, then the blue gene is autosomal. If there are only blue males, then it is X-linked. 4. (8) Suppose that a gene is a suppressor of the expression of the wrinkled pea allele that Mendel studied; remember that round is dominant to wrinkled. The suppressor has two alleles S and s. ss peas are round regardless of the genotype of the round/wrinkled gene. The round/wrinkled phenotype is not affected in SS and Ss peas. You begin with two pure-breeding lines, one homozygous for s and round and the other homozygous for S and wrinkled. You then create the F
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bioeMCB C142-fall06-mt1-Slatkin-soln - MCB 142/ IB 163...

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