7 03 FALL 2009 PROBLEM SET 1 Due September 23 2008 1 15 points You have isolated a collection of yeast mutants that form dark tan colonies wild type yeast are white Dark mutants 1 5 are MATa and mutants 6 10 are MAT Your analysis begins by pairwise mating of each mutant to a wild type strain and to the mutants of the opposite mating type The color of the colonies of the resulting diploids are shown in the table below a Wildtype Mutant 1 Mutant 2 Mutant 3 Mutant 4 Mutant 5 Wildtype White White White White White White Mutant 6 White Dark White White Dark White Mutant 7 White White White White White Dark Mutant 8 Dark Dark Dark Dark Dark Dark Mutant 9 White White White White White Dark Mutant 10 White Dark White White Dark White a Which of the mutants are dominant and which are recessive 2ps b Organize the mutants into complementation groups genes indicating any ambiguities 9 pts c Based on these complementation data what is the minimum number of genes represented by this collection of dark mutants What is the maximum number of genes 4 pts 2 18 points In a large scale breeding population two female flies with vestigial wings shortwinged flies arise from different parents You would like to know whether the two mutations that caused this vestigial wing phenotype are in the same gene or in different genes Assume that you have an unlimited number of true breeding flies with normal wings Describe a set of crosses you would perform to make this determination and their outcomes In your description please indicate a set of circumstances that would prevent you from easily making this determination 1 3 32 points Say fur color in mice is determined by 2 genes One gene determines what color pigment is produced and another gene determines whether or not any pigment is produced at all Suppose black fur is dominant to brown fur but a mutation in the other gene prevents pigment of either color from being produced so the mice are white You cross a truebreeding brown mouse with a true breeding white mouse a Determine the ratio of each color mouse in the F2 generation if the F1 progeny are black 4 pts b Determine the ratio in the F2 generation if the F1 progeny are white Assume the parental white mice had only one mutation 4 pts c When you performed this cross all the F1 progeny were black These all have the same genotype but the black mice in the F2 generation have more than one genotype You wish to determine the genotype of one of the black F2 mice so you back cross to a heterozygous F1 mouse For each possible genotype determine the expected ratio of fur colors in the progeny 10 pts d You get 40 progeny from your test cross of which 32 are black and 8 are brown You think you know the genotype but your lab partner thinks it could still be two genotypes Use the chi square test to determine if you can reject one of the remaining hypotheses The table below gives chi square values for 1 2 and 3 degrees of freedom Use the convention that for p 0 05 there is a statistically significant difference between the observed results and the results expected for a given model and therefore we can reject the model on the basis of the experimental data 14 pts p value df 1 df 2 df 3 995 000 01 07 975 000 05 22 0 9 016 21 58 0 5 46 1 4 2 4 0 1 2 7 4 6 6 3 0 05 3 8 6 0 7 8 0 025 5 0 7 4 9 3 0 01 6 6 9 2 11 3 0 005 7 9 10 6 12 8 2 4 31 points Consider a cross of two mice whose genotypes for five independently segregating traits are Strain 1 DdEEFFGgHH and Strain 2 DdEeffGgHH Capital letters indicate the dominant alleles and the all of the traits are independently scoreable a How many different types of gametes can each parent produce 4 pts b How many different phenotypes can result from this cross How many different genotypes 9 pts c What fraction of the progeny will be phenotypically identical to the first parent To the second parent 4 pts d i What fraction of the progeny will be genotypically identical to the first parent What fraction will be identical at four of the five loci 4 pts ii What fraction of the progeny will be genotypically identical to the second parent At four loci 4 pts e One of the progeny of the above cross has the phenotype d E F g H What cross should you perform to determine the genotype 6 pts 3 5 32 points The following is a pedigree from a family with a rare autosomal recessive disorder In this question R represents a dominant allele and r represents a recessive allele Please note that this imaginary pedigree is from a society in which brother sister marriages are common B A Not affected Affected C D E F G a What is the probability that individual A has genotype Rr 2 pts b What is the probability that individual E has genotype Rr 2 pts c i What is the probability that G when born will be affected 6 pts ii What is the probability that G will have genotype Rr 9pts Suppose that individual G is born and does not have the disease d What is the probability that individual G has genotype Rr 4 pts e What is the probability that individual E has genotype Rr given that G has genotype Rr 9 pts 4 7 03 FALL 2009 PROBLEM SET 2 Due October 2 2009 1 24 points You are studying three autosomal mutations in the fruit fly Drosophila melanogaster The cw mutation gives the recessive curly wing phenotype wild type flies cw are straight winged the sh mutation gives the recessive short bristled phenotype wild type flies sh are long bristled and the nh mutation gives the recessive no bristled phenotype wild type flies nh are long bristled a You mate a homozygous nh cw sh fly which is no bristled and straight winged to a truebreeding long bristled and curly winged fly to obtain an F1 generation List all phenotypic categories of the flies in the F1 generation and the ratio in which these phenotypic categories are found in the F1 generation The possible phenotypic classes are short bristled and curlywinged long bristled and straight winged short bristled and straight winged long bristled and curly winged no bristled and curly winged no bristled and straight winged b To do a proper three factor cross you need to create an F2 generation by mating F1 females to a specific true breeding male What is the phenotype of the true breeding male fly you would choose as the parent for the F2 generation You do a proper three factor cross and in the F2 generation you obtain the following number of …
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