PopGenProblemSet_Fall2008 - Name _ BioEE 2780 Section _...

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Name _______________________ Section _________ 1 BioEE 2780 Population Genetics Problem Set The completed problem set is due in your section on November 4/5/6. Late assignments will not be accepted. This assignment is worth a total of 16 points and you must show your work to receive full credit. Problem 1: Arctic foxes on the island of Jan Mayen exhibit striking polymorphism in their coat coloration. There are three forms on the island: white, black, and gray. You are a graduate student interested in studying the evolution and population genetics of this coat color polymorphism. A collaborater doing field work on the island sends you data on genotype and coat color phenotype and for 137 foxes. You suspect that natural selection plays a role in maintaining this polymorphism on the island, but your advisor is skeptical. You show your advisor the new data and she says is, “The first thing you need to do to convince me about your ‘selection’ hypothesis is check for Hardy-Weinberg Equilibrium!” Arctic Fox Data: Jan Mayen Island Genotype Color Number AA White 48 Aa Gray 52 aa Black 37 (a) Briefly explain why your advisor wants to know about HWE in this population. Why is this informative regarding your hypothesis that natural selection shapes the frequency of color polymorphism among arctic foxes on Jan Mayen Island? Being the dutiful grad student that you are, you immediately do as your advisor suggests. Calculate allele frequencies and expected genotype frequencies for this sample and address the following questions: How do observed and expected numbers of genotypes differ? Does it appear that the fox population is in Hardy-Weinberg equilibrium? Does this support your assertion about natural selection acting on fox populations, or your advisor’s skepticism about it? Explain why. Assuming the fox population is not in HWE (regardless of the observed data) which evolutionary processes other than selection could account for this? (Hint: there are four such processes.) (there is space to answer on the next page)
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Name _______________________ Section _________ 2 Jan Mayen is a mountainous, volcanic island partly covered by glaciers. It consists of two parts connected by a narrow isthmus. On closer inspection of your colleague’s field records, you discover that 65 of the foxes were from the north end of Jan Mayen, and the remaining 72 foxes were from the south end. Phenotypes for the two “populations” are:
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PopGenProblemSet_Fall2008 - Name _ BioEE 2780 Section _...

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