7 03 Fall 205 Exams Answers 1 of 93 Name 7 03 Exam One 2005 Name Exam starts at 11 05 am and ends at 11 55 am There are 7 pages including this cover page Please write your name on each page Only writing on the FRONT of every page will be graded You may use the backs but only as scratch paper Question 1 24 pts Question 2 30 pts Question 3 30 pts Question 4 16 pts TOTAL out of 100 1 9 5 07 7 03 Fall 205 Exams Answers 2 of 93 Name 1 24 pts You are studying two recessive mutations in the fruit fly Drosophila melanogaster The hb mutation causes flies to have hairy backs wild type flies have hairless backs The tl mutation causes flies to have thick legs wild type flies have thin legs You mate females from a true breeding strain with hairy backs and normal legs to males from a true breeding strain with normal backs and thick legs F1 females are then mated to males that have hairy backs and thick legs to produce F2 progeny If you analyzed 500 MALE progeny in the F2 generation how many flies of each possible phenotypic class would you expect given that a 8pts The two traits are determined by two unlinked autosomal genes hairy thick hairy thin hairless thick hairless thin b 8pts The two traits are determined by two completely linked genes on the X chromosome hairy thick hairy thin hairless thick hairless thin c 8pts The two traits are determined by two autosomal genes that are 20 cM apart hairy thick hairy thin hairless thick hairless thin 2 9 5 07 7 03 Fall 205 Exams Answers 3 of 93 Name 2 30 pts The following pedigree shows the inheritance two different rare traits Each trait is determined by a different gene The presence of Trait 1 is indicated by dots and the presence of Trait 2 is indicated by vertical lines Note that no single individual displays both traits a 6pts What mode s of inheritance is are consistent with each of the traits segregating in this pedigree Your choices are autosomal recessive autosomal dominant X linked dominant X linked recessive Assume no new mutations and complete penetrance Trait 1 dots Trait 2 vertical lines b 6pts State whether the two traits in the pedigree are linked or not linked or if it is inconclusive given these data c 6pts What is the probability that the child indicated with a question mark will show at least one of the two traits Show your work 3 9 5 07 7 03 Fall 205 Exams Answers 4 of 93 Name Consider this new pedigree which shows the inheritance of two different rare traits Each trait is determined by a different gene The presence of Trait 3 is indicated by horizontal lines and the presence of Trait 4 is indicated by shading Note that no single individual displays both traits d 6pts What mode s of inheritance is are consistent with each of the traits segregating in this pedigree Your choices are autosomal recessive autosomal dominant X linked dominant X linked recessive Assume no new mutations and complete penetrance Trait 3 horizontal lines Trait 4 shading e 6pts State whether the two traits in the pedigree are linked or not linked or if it is inconclusive given these data 4 9 5 07 7 03 Fall 205 Exams Answers 5 of 93 Name 3 30 pts You are studying three mutations in yeast The first mutation causes the Ser phenotype of being unable to grow without serine in the medium The second mutation causes the His phenotype of being unable to grow without histidine in the medium The third mutation causes a small colony phenotype Wild type yeast are Ser His and big You mate a Ser haploid mutant yeast to a His small haploid mutant yeast You induce sporulation of the resulting diploid and obtain the following tetrad types The number of tetrads of each type that you get out of a total of 100 are shown after the tetrad type Tetrad Type A Ser His big Ser His small Ser His big Ser His small 9 tetrads of this type Tetrad Type B Ser His big Ser His big Ser His small Ser His small 90 tetrads of this type Tetrad Type C Ser His big Ser His small Ser His big Ser His small 1 tetrad of this type a 4pts Which Tetrad Types are TTs NPDs and PDs with respect to the His and size genes TT NPD PD b 4pts Are the His and size loci linked If so what is the genetic distance between them 5 9 5 07 7 03 Fall 205 Exams Answers 6 of 93 Name c 4pts Which Tetrad Types are TTs NPDs and PDs with respect to the Ser and size genes TT NPD PD d 4pts Are the Ser and size loci linked If so what is the genetic distance between them e 4pts Which Tetrad Types are TTs NPDs and PDs with respect to the Ser and His genes TT NPD PD f 4pts Are the Ser and His loci linked If so what is the genetic distance between them g 6pts Draw a genetic map showing the correct relative order of the Ser His and size loci If one of the loci is unlinked from the other two draw it on a separate chromosome 6 9 5 07 7 03 Fall 205 Exams Answers 7 of 93 Name 4 16 pts You are studying a recessive trait in a diploid rodent species in which XX organisms are female and XY organisms are male This trait is determined by a single gene but you have no idea where in the genome this gene is located This rodent has 20 000 distinct genes in its genome 400 of which are found on the X chromosome a 4pts Given this information give your best estimate of the probability that the trait you are studying is X linked b 12pts You mate a female rodent displaying the trait to a wild type male You then mate an F1 female to a wild type male to produce F2 offspring and analyze only the F2 males The first three F2 male offspring display the wild type phenotype Given that the first three male F2 offspring show the wild type phenotype determine the probability that the trait you are studying is X linked Show all steps of your work using clear labels 7 9 5 07 7 03 Fall 205 Exams Answers 8 of 93 Name KEY 7 03 Exam One 2005 Name KEY Exam starts at 11 05 am and ends at 11 55 am There are 7 pages including this cover page Please write your name on each page Only writing on the FRONT of every page will be graded You may use the backs but only as scratch paper Question 1 24 pts Question 2 30 pts Question 3 30 pts Question 4 16 pts TOTAL out of 100 1 9 5 07 7 03 Fall 205 Exams Answers 9 …
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