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Exam2_2013KEY_FINAL_new_PDF

# 9 01 q 2 x 10601 000447 p 1 000447 09955

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Unformatted text preview: . Fill out the following table based on these data (4 points): Polymorphism Nonsyn Syn Divergence 5 1 0 2 7b. Describe the pattern you found, what kind of test for selection you could perform on these data and given the pattern, what you can infer about the evolution of this gene (6 points): An excess of nonsynonymous divergent substitutions is observed, I would perform a McDonald ­Kreitman test to determine if the ratios differed within and between species. We can probably infer that positive selection drove rapid fixation of nonsynonymous substitutions here. 6 ECOL 335 Evolutionary Biology NAME_____KEY________________ Sect#_____ Exam 2 Spring 2013 March 6, 2012 8. In a population of saguaro cacti, the relative fitness of a recessive genotype is 0.9, and the mutation rate to the recessive allele is 2 x 10 ­6. If the population is allowed to come to equilibrium, what allelic frequencies can be predicted? Show this in terms of mathematical calculations and in your own words (4 points). Because selection and mutation are acting in opposite ways, an equilibrium is predicted: q = √u/s u = 2 x 10 ­9 s = 1 – 0.9 = 0.1 q = √(2 x 10 ­6/0.1) = 0.00447 p = 1 – 0.00447 = 0.9955 9. In an Anna’s hummingbird population, the average bill length is 1 inch, there is a normal (bell ­shaped) distribution of bill lengths. A frost kills all plants with nectar tubes less than 1.5 inches and you find that after a few months, the only hummingbirds breeding (still within the same generation) have an average bill length of 1.75 inches on average. You find, one generation (after these birds breed), that the mean of...
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