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2006midterm2Akey

# 2006midterm2Akey - BICD100 2006 Midterm 2 KEY TO VERSION A...

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1 BICD100 2006 Midterm 2 (2/22/06) : KEY TO VERSION A 1.) Certain varieties of flax (the plant) show different resistances to specific races of the fungus called flax rust. Flax variety 770B is resistant to rust race 22 but susceptible to race 24, whereas flax variety Bombay is resistant to rust race 24 but susceptible to race 22 (both varieties are true breeding for these traits). When 770B is crossed to Bombay, the F1 progeny are all resistant to both rust races. In one study where these F1 progeny were selfed, the following progeny were obtained: resistant to race 24 only: 63 resistant to race 22 only: 58 resistant to both races: 184 susceptible to both races: 15 a. Choose the hypothesis that best explains these results (circle one)(4 pts): i. Susceptibility to race 22 and race 24 are recessive traits controlled by two linked genes ii. Susceptibility to race 22 and race 24 are dominant traits controlled by two linked genes iii. >> Susceptibility to race 22 and race 24 are recessive traits controlled by two unlinked genes iv. Susceptibility to race 22 and race 24 are dominant traits controlled by two unlinked genes b. Test your hypothesis using the Chi squared test. Show your work for full or partial credit, and include in your answer the value of Chi squared, the associated p value, and your conclusion (accept hypothesis or reject it) (14 pts). χ 2 = [(O-E) 2 /E] = (63 - 60) 2 /60 + (58 – 60) 2 /60 + (184-180) 2 /180 + (15 – 20) 2 /20 = 0.15 + 0.07 + 0.09 + 1.25 = 1.56 At 3 degrees of freedom, this corresponds to a p value between 0.5 and 0.9 Conclusion: accept hypothesis -> genes are unlinked

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2 2.) Wild type colonies of baker’s yeast ( S. cerevisiae ) are white. A yeast geneticist isolates 4 new haploid mutants that make pink colonies (mutants 1-4 in table to the right) and one that makes red colonies (mutant 5 in table). After determining that all 5 mutations are recessive, she proceeds to cross the different haploid mutants together in several pairwise combinations. For each cross, the phenotype of diploid progeny colonies is shown in the table.
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2006midterm2Akey - BICD100 2006 Midterm 2 KEY TO VERSION A...

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