PS4_Key - BICD100 Genetics Fall 2005 Reinagel Problem Set...

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BICD100 Genetics Fall 2005 Reinagel Problem Set 4: Chromosomal Basis of Inheritance ANSWER KEY 1. You have two mutant pure-breeding strains of fruit flies. One mutant strain has curly wings (c recessive mutant = curly wings, C dominant wild type = straight wings). The other mutant strain has stubby wings (s recessive mutant = stubby, S dominant wild type = long wings). Assume that these mutations are in two different genes and the genes do not interact functionally (no epistasis, suppression, redundancy). You cross a purebred female with long, curly wings to a purebred male with stubby, straight wings to produce F1 flies. You cross F1 flies to one another to obtain an F2 generation. You have several different (alternative) models you want to compare. For each model described below, predict the phenotypes of males and females in the F1 generation and in the F2 generation, and state the ratios in which the phenotypes should occur in each cross. a. Your model is that both curly and stubby are autosomal on two different autosomes Genotypes ♀ phenotypes ♂ phenotypes P ccSS ♀ x CCss ♂ curly long x straight stubby F1 CcSs all straight, long all straight, long F2 9 C_S_ 9 straight long 9 straight long 3 C_ss 3 straight stubby 3 straight stubby 3 ccS_ 3 curly long 3 curly long 1 ccss 1 curly stubby 1 curly stubby b. Your model is that curly is autosomal and stubby is X-linked Genotypes ♀ phenotypes ♂ phenotypes P ccX S X S x CCX s Y ♂ curly long x straight stubby F1 CcX S X s ♀, CcX S Y ♂ all straight, long all straight, long F2 CX S cX S CY cY CX S CCX S X S CcX S X S CCX S Y CcX S Y cX S CcX S X S ccX S X S CcX S Y ccX S Y CX s CCX S X s CcX S X s CCX s Y CcX s Y cX s CcX S X s ccX S X s CcX s Y ccX s Y      F2 females F2 males 3 straight, long 3 straight long 1 curly, long 3 straight stubby 1 curly long 1 curly stubby
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BICD100 Genetics Fall 2005 Reinagel c. Your model is that curly is X-linked and stubby is autosomal Genotypes ♀ phenotypes ♂ phenotypes P X c X c SS ♀ x X C Yss ♂ curly long x straight stubby F1 X C X c Ss ♀, X c YSs ♂ all straight, long all curly, long F2 SX c sX c SY sY SX C SSX C X c SsX C X c SSX C Y SsX C Y sX C SsX C X c ssX C X c SsX C Y ssX C Y SX c SSX c X c SsX c X c SSX c Y SsX c Y sX c SsX c X c ssX c X c SsX c Y ssX c Y      F2 females F2 males 3 S_ X C _ long, straight3 S_ X C Y long, straight 1 ss X C _ stubby, straight
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PS4_Key - BICD100 Genetics Fall 2005 Reinagel Problem Set...

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