2012 Quiz 2 Key

2012 Quiz 2 Key - Biol241 2012 Quiz 2(20 points) ...

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Unformatted text preview: Biol241 2012 Quiz 2 (20 points) Name:__________________________ Purdue ID:__________________________ 1) Assume that three pairs of alleles are found in Drosophila: +/x, +/y, and +/z. As shown by the symbols, each non ­wild allele is recessive to its wild ­type allele. A cross between female heterozygous at these three loci and homozygous recessive males (xxyyzz) yields the following progeny phenotypes: + + + 31 x y z 38 x + z 430 + y + 441 x y + 27 + + z 32 x + + 1 + y z 0 a. What is the gene order on the chromosome (3 points)? The order is x z y (y z x). b. Calculate the map distances (in map units) between the genes and draw a map (4 points). The distance between x and z is (27+32+1)/1000=0.06 or 6 m. u. The distance between z and y is (31+38+1)/1000=0.07 or 7 m. u. x 6 m.u. z 7 m.u. y  ­+ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­+ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­+ ­ ­ ­ ­ c. Calculate coefficient of coincidence and interference (3 points). C.C.=1/1000*0.06*0.07=0.238 I=1 ­C.C.=0.762 Biol241 2012 Quiz 2 (20 points) Name:__________________________ Purdue ID:__________________________ 2) In Neurospora, a cross a b X + + is made and 100 linear asci from this cross are analyzed. The results are shown below. 1 2 3 4 5 6 ab a+ ab ab ab a+ ab a+ a+ +b ++ +b ++ +b ++ ++ ++ ++ ++ +b +b a+ ab ab 71 1 18 1 8 1 a. What is the genetic distance (in map units) between a and centromere (2 points)? The genetic distance is 1/2*(1+8+1)/100=0.05 or 5 m.u. b. What is the genetic distance (in map units) between b and centromere (2 points)? The genetic distance is 1/2*(18+8+1)/100=0.135 or 13.5 m.u. c. Are a and b linked? If yes, what is the genetic distance between a and b (2 points)? NPD is much less than PD, thus a and b are linked. The genetic distance between a and b is (½*(18+1+1)+1)/100=0.11 or 11 m.u. d. Draw a map of a , b, and centromere(s) (2 points). c 5 m.u. a 11 m.u. b  ­ ­ ­ ­o ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­+ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­+ ­ ­ ­ ­ ­ e. Diagram the crossover event responsible for ascus 5 (2 points). The best answer is this one a b a b + + + + But I will accept this one as well a b a b + + + + ...
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