7 03 Exam 1 Name TA Alex Bagley Alice Chi Dave Harris Doug Mills Rishi Puram Bethany Redding Max Juchheim Nate Young Section time Exam starts at 11 05 and ends at 11 55 There are seven pages including this cover page Please write your name on each page Please Look over the entire exam so you don t spend too much time on hard questions leaving easy questions unanswered Check your answers to make sure that they make sense To help us give partial credit show your work and state any assumptions that you make Question 1 Question 2 26 points 36 points Question 3 38 points Name 1 Consider the following autosomal Drosophila traits caused by recessive alleles bent wings bn short legs sh and orange eyes or You cross two true breeding lines to produce F1 flies all of which have the wild type phenotype strait wings long legs and red eyes F1 females are then mated to triply homozygous males with bent wings short legs and orange eyes Among 100 progeny from this cross you observe the following phenotypes Phenotype strait wings long legs and red eyes bent wings short legs and orange eyes strait wings short legs and red eyes bent wings long legs and orange eyes strait wings long legs and orange eyes bent wings short legs and red eyes strait wings short legs and orange eyes bent wings long legs and red eyes Number 10 14 26 30 8 6 2 4 a 6 points What were the genotypes of the two true breeding parental lines that were crossed b 12 points Draw a genetic map showing the order and relevant distances in cM of the bn sh and or markers 2 Name c 8 points A colleague calls to tell you she plans to carry out the following two factor cross A true breeding line with bent wings will be crossed to a true breeding line with short legs unless specified other traits appear normal F1 flies will then crossed to a true breeding strain with bent wings and short legs Your colleague wants to know what proportion of the progeny from this cross will have bent wings and short legs What would you tell her 2 The pedigree shows inheritance of an X linked recessive trait Assume the trait is completely penetrant a 4 pts What is the probability that the female designated 1 is a carrier for the trait b 6 pts If the child indicated by is a boy what is the probability he will be affected by the trait 3 Name c 6 pts If the child indicated by is a girl what is the probability she will be affected by the trait d 8 pts If the child indicated by is affected by the trait what is the probability that the couple s next child will be affected by the trait e 12 pts If the child indicated by is not affected by the trait calculate the new probability that the female designated 1 is a carrier for the trait 4 Name 3 You have isolated two different yeast mutants called cys1 and cys2 that cannot synthesize the amino acid cysteine and therefore require cysteine added to the medium for growth i e they are Cys a 4 points You mate a call cys1 mutant to a cys2 mutant The resulting diploids don t require cysteine i e they are Cys What does this tell you about the cys1 and cys2 mutations Next you sporulate the diploid from part a Among the 50 tetrads analyzed three different tetrad types are found Type Number 4 Cys 39 3 Cys 1 Cys 10 2 Cys 2 Cys 1 b 6 points Say that you want a cys1 cys2 double mutant What is the easiest way to obtain such a mutant without further analysis c 6 points You choose one of the tetrads for further analysis and the four spores have the following properties Spore 1 MATa Cys Spore 2 MATa Cys Spore 3 MAT Cys and Spore 4 MAT Cys You carry out the matings that are possible and find that the diploid produced by mating Spore 2 to Spore 3 is Cys while the diploid produced by mating Spore 2 to Spore 4 is Cys Which spore is the double mutant Explain your reasoning 5 Name d 6 points Given the number of terads of each type what is the distance between the cys1 and cys2 mutations You have isolated a mutation that you call cysX that activates an alternative pathway for cysteine synthesis A cysX mutation on its own is Cys and when a cysX mutation is combined with a cys1 mutation the double mutant is Cys e 8 points Describe the cross you would perform and the interpretation of the outcome that you would use to determine whether cysX is dominant or recessive f 8 points Say that cysX is 5 cM away from cys1 In a cross of a MATa cysX mutant to a MAT cys1 mutant what types of tetrads in terms of the proportion of Cys Cys would you expect to find and how many of each type would you expect from a total of 50 tetrads 6 Grading section Question 1 26 points Question 2 36 points Question 3 38 points Total 7 7 03 Exam 1 Name TA circle one Alex Bagley Doug Mills Alice Chi Rishi Puram Dave Harris Bethany Redding Max Juchheim Nate Young Section time Exam starts at 11 05 and ends at 11 55 There are eight pages including this cover page Please write your name on each page Please Look over the entire exam so you don t spend too much time on hard questions leaving easy questions unanswered Check your answers to make sure that they make sense To help us give partial credit show your work and state any assumptions that you make Question 1 26 points Question 2 36 points Question 3 38 points Name 1 Consider the following autosomal Drosophila traits caused by recessive alleles bent wings bn short legs sh and orange eyes or You cross two true breeding lines to produce F1 flies all of which have the wild type phenotype strait wings long legs and red eyes F1 females are then mated to triply homozygous males with bent wings short legs and orange eyes Among 100 progeny from this cross you observe the following phenotypes Phenotype Number strait wings long legs and red eyes 10 bent wings short legs and orange eyes 14 strait wings short legs and red eyes 26 bent wings long legs and orange eyes 30 strait wings long legs and orange eyes 8 bent wings short legs and red eyes 6 strait wings short legs and orange eyes 2 bent wings long legs and red eyes 4 a 6 points What were the genotypes of the two true breeding parental lines that were crossed We can determine the genotypes of the parental flies by looking at the two highest classes of progeny in the F2 These classes are the Parental Classes Based on these classes we can determine that the original true breeding strains were …
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