Problem Set 5 - LS4 Problem Set 5, 2010 Mutagenesis Screens...

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LS4 Problem Set 5, 2010 Mutagenesis Screens Corresponding Lectures: November 24 and 29, December 1 Corresponding Reading: , Beddington paper; Haffter and Nusslein-Volhard paper; Horvitz paper (available on the course website). Corresponding Quiz: November 29-December 3 Problem 1. In a Drosophila screen, a cross between two F2 siblings results in ¼ mutant progeny, as expected from a normal, recessive mutation. A) What percentage of offspring from that cross will be heterozygous carriers for the mutant allele? What percentage will be homozygous wild-type? B) If you cross one of the F3 mutants to a non-mutant sibling, what are the chances that the cross will result in mutant progeny? C) If a cross between a mutant and one a randomly chosen sibling results in mutant progeny, what percentage of the progeny of this cross will be mutant? Problem 2. A haploid yeast strain has a mutation in the leu1 gene, making it auxotrophic for leucine. W mates this strain to a wild-type strain of the opposite mating type, creating a diploid strain heterozygous for leu1. In this strain, W knocks out one copy of a gene required to make adenine, ade3, by homologous recombination. Both of these mutations are recessive, so the diploid can grow on minimal media. leu1 and ade3 are on different chromosomes. W then induces these diploid cells to sporulate and form haploid spores. A) What fraction of the haploid spores will be able to grow on minimal media? B) what fraction will grow on minimal media supplemented with leucine? C) what fraction will grown on minimal media supplemented with adenine? Problem 3. B is performing a gynogentic diploid screen in zebrafish and finds three mutants from three different mothers with the identical phenotype: they have only one eye. Mutant A is seen in 15 out of 50 siblings in the gynogenetic clutch, mutant B is homozygous in 6 out of 80 gynogenetic diploid siblings, and mutant C is homozygous in 3 out of 40 gynogentic diploid siblings. A) Which mutation is closest to the centromere? B)
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This note was uploaded on 02/15/2012 for the course PMB 13 taught by Professor Freeling during the Spring '09 term at University of California, Berkeley.

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Problem Set 5 - LS4 Problem Set 5, 2010 Mutagenesis Screens...

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