WalshKey

# WalshKey - Genetics 320(EEB/MCB Final Exam Key(Walsh(6 10...

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Genetics 320 (EEB/MCB) Final Exam Key (Walsh) (6) [ 10 points ] Consider a cross between two parents: AaBbCCdd and AaBbCcDd where all loci are unlinked. (a) What is the probability of an AaBbCcDd offspring? = (1/2)(1/2)(1/2)(1/2) = 1/16 (b) How many offspring do you need to sample to ensure a 90 percent probability that at least one is AaBbCcDd ? Prob(all n are not AaBbCcDd) = .10 or (1-1/16) n = 0.10, or n = ln (0.10)/ln(15/16 = 36 (6) [ 10 points ] Short answer, i.e., one or two SHORT sentences (5 points each). (a) Why are males more likely to be color blind than females? Red-Green color blindness is recessive and on the X. Males need only a single bad X to be color, females need two. (b) Why is an X0 fly (a single X, no Y) a male? Sex determined in flies by X: autosome ratio. Single X to normal autosomes = male. (c) Why is an XO human female? Sex is determined in mammals by presence/absence of a Y. No Y = female. (7) [10 points ] Suppose the recombination frequnecy between loci A and B is 0.2. In a population you observ the following gamete frequencies: AB 0.3 Ab 0.4 aB 0.1 ab 0.2 (a)

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## This note was uploaded on 06/16/2008 for the course ECOL 320 taught by Professor Weinert during the Spring '07 term at Arizona.

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WalshKey - Genetics 320(EEB/MCB Final Exam Key(Walsh(6 10...

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