PS2 - CH388 Fall 2007(AY08-01 Problem Set#2 Linkage/mapping...

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CH388 Fall 2007 (AY08-01) Problem Set #2 Linkage/mapping; Cytogenetics APPROVED SOLUTION The following problem set is worth 75 points. Problems are due to the instructor NLT 1600 on 27 Sept 07. A Documentation of Written Work Coversheet must be initialed, signed, and attached. Any assistance outside of the instructor must be documented and properly acknowledged. This includes websites, textbooks, personnel and resources outside of original thought. For assistance or further guidance, see your instructor. For full credit, show all work, and calculations. Use the correct symbols as outlined in your textbook. Attach additional worksheets as needed. LINKAGE 1. (20 pts) An autosomal recessive gene tra , when homozygous, transforms a Drosophila female (X/X) into a phenotypic male. All such “transformed” males are sterile. The gene is without effect in males (X/Y). A cross is made between a female heterozygous at the tra locus and a male homozygous recessive at the same locus ( tra/tra ). (a) What is the expected sex ratio in the F 1 ? ¾ males : ¼ females (b) Show the P 1 genotype for the male and female cross and fill in the F 1 crossing table. For each resulting cross in the F 1, identify the genotype and state whether the flies are normal female, normal male, female, male, or transformed males. Female Male 1 P 1 Gametes X/X, +/ tra x X/Y, tra/tra normal female normal male X + X tra X tra Y tra X/Y, tra/tra male X/Y, +/ tra male Y tra X/X, tra/tra transformed” males X/X, +/ tra female X tra X tra X + The F1 phenotypic proportions appear ¾ males : ¼ females. F 1
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CH388 Fall 2007 (AY08-01) Problem Set #2 Linkage/mapping; Cytogenetics APPROVED SOLUTION (c) For the F2, cross the given female (X + or X tra ) with gamete possibilities from a X/Y, +/ tra male. Identify the genotype and state whether the flies are normal female, normal male, female, male, or transformed males. Female Males (d) What is the expected genetic contribution of transformed F 1 males to the future gametes in the F 2 ? The transformed F 1 males are sterile and do not contribute gametes to the F 2 . 2 X/X, tra/tra “transformed” male X/X, +/ tra female X tra X/Y, tra/+ male X/Y, +/+ male Y + X/Y, tra/tra male X/Y, +/ tra male Y tra X/X, +/ tra female X/X, +/+ Normal female X + X tra X + X/X, +/ tra x X/Y, +/ tra female males F 2
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CH388 Fall 2007 (AY08-01) Problem Set #2 Linkage/mapping; Cytogenetics APPROVED SOLUTION SEX-LINKAGE 2. (10 pts) A recessive sex-linked gene h prolongs the blood-clotting time, resulting in what is commonly called “bleeder’s disease” (hemophilia). From the information in the pedigree, answer the following questions. (a) What is II 2’s genotype?
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This note was uploaded on 04/15/2008 for the course CH 388 taught by Professor Eslinger during the Fall '08 term at West Point.

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PS2 - CH388 Fall 2007(AY08-01 Problem Set#2 Linkage/mapping...

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