Gen371 Practice 4 Answers

Gen371 Practice 4 Answers - Gen371 Practice 4 Answers...

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1/26/11 4:19 PM Gen371 Practice 4 Answers Page 1 of 16 http://courses.washington.edu/au371mkr/resources/problems/problems_04-key.html Practice problems set 4 -- answers 1. A researcher has created a new transposon system in Drosophila . He still is using P[w + ] and Jump-starter (i.e., P[TNase]). However, their genomic locations may be different from what you have seen, and the 2nd and 3rd chromosome markers are new: On chromosome II: GR = green body ( dominant , homozygous lethal); gr = normal (tan) body (recessive) On chromosome III: SP = split wings ( dominant , homozygous lethal); sp = normal wings (recessive) He generates male flies containing both Jump-starter and P[w + ], mates them to homozygous recessive females, and from the progeny he picks red-eye, normal (tan) body, split wing males as potential mutants. (Assume that he didn’t make mistakes!) (a) To generate male flies containing both Jump-starter and P[w + ], the researcher must have used flies with what genotypes? Logic: Since he avoided the green-body phenotype in his potential mutant flies, we can infer that GR must be the dominant marker linked to P[TNase], so it must be on the 2nd chromosome. Therefore, the marker that is used to screen for jumps (i.e., the marker that must segregate away from P[w+] unless there has been a transposition event) must be on the 3rd chromosome. (b) One potential mutant, when mated with white-eyed females, had male progeny that were all red-eyed and female progeny that were all white-eyed. Suggest an explanation for this outcome. The transposon must have jumped onto the Y chromosome: female progeny of the mutant fly would be X w X w (white-eyed) and male progeny would X w Y P[w+] , red-eyed. (c) From the transposon mutagenesis, the researcher has identified mutations at two loci: a mutation at locus G results in decreased resistance to pesticide compared to wild type, while a mutation at locus H results in increased resistance. Flies that were heterozygous at both loci were crossed to each other. The progeny were: 90 flies showed wild type levels of pesticide resistance 40 flies were less resistant than wild type 30 flies were more resistant than wild type For both loci, state whether the mutant alleles are dominant or recessive: Locus G mutant allele: Dominant? Recessive ? (circle one) Locus H mutant allele: Dominant? Recessive ? (circle one) Give the genotypes of the progeny flies in (a) to explain the phenotype proportions. (Underline dominant alleles as always.) 9/16 G? H? (wild type resistance) 3/16 G?hh (increased resistance) 3/16 gg H? (decreased resistance) Home Course mechanics Help hours Calendar Syllabus Lectures, Podcasts Quiz Sections Practice problems Exams GoPost Send email to class Useful links The Gradiator
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1/26/11 4:19 PM Gen371 Practice 4 Answers Page 2 of 16 http://courses.washington.edu/au371mkr/resources/problems/problems_04-key.html 1/16 gghh (decreased resistance) ...giving a 9:3:4 overall ratio of wildtype : increased resistance : decreased resistance.
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This note was uploaded on 03/31/2011 for the course GENOME 371 taught by Professor Unsure during the Spring '03 term at University of Washington.

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Gen371 Practice 4 Answers - Gen371 Practice 4 Answers...

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