SP08-SQ2Trenham

SP08-SQ2Trenham - 1B Trenham Study Questions # 2 Spring...

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1B Trenham Spring 2008 Study Questions # 2 Population Genetics and Natural Selection 1. A scientist is studying the frequency of color alleles and genotypes in the peppered moth around the city of Manchester in England. In 1980, she finds that the frequency of the a allele in that population is 0.2. Peppered moths are an annual species, with one generation per year. If Hardy-Weinberg conditions apply to this population, the expected frequencies for aa, Aa and AA genotypes the next year would be: frequency of aa genotype = frequency of Aa genotype = frequency of AA genotype = This scientist comes back to this population in 1995, and records the colors of 4000 moths. She finds that 12% of the moths this generation are gray, and the rest (88%) are dark. How do these results compare to the results you predicted above? Is this population in Hardy-Weinberg equilibrium? Given what you know about this species, suggest a reason for this result. 2. Imagine that budgerigars practice strict positive assortative mating, such that green birds only mate with green birds, while blue birds only choose blue mates. A breeder places 40 blue birds and 60 homozygous green birds together in a large flight cage. In this parental generation, what is the frequency of the y allele? of the Y allele? If the birds practiced strict positive assortative mating, what would be the frequency of the YY, Yy and yy genotypes in the offspring generation? (Hint: allow each mating pair to make 4 babies and count up the offspring genotypes.) What would be the frequency of the y and Y alleles in the offspring generation? How do these results compare to the genotype frequencies expected if this budgie population fit all of the required conditions for Hardy-Weinberg equilibrium? -1-
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3. In contrast to the last question, imagine that all budgerigars prefer green to blue mates. As a result, green birds are more likely to obtain high quality, experienced mates, while blue birds would be more likely to end up with poor, inexperienced mates, or with no mate at all. In this situation, which phenotype is likely to have higher reproductive success? How would the process described here affect the frequency of blue and green phenotypes in successive generations, as opposed to the distribution of phenotypes predicted by a Hardy-Weinberg equilibrium model? 4. Which of the following phenotypic traits provide an example of quantitative inheritance (more than one answer is possible)? Hint : you know something about the genetic basis of some of these characters; for the others, what would you predict about the shape of the distribution? How do the shapes of the distributions for quantitative characters and single gene characters differ?
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SP08-SQ2Trenham - 1B Trenham Study Questions # 2 Spring...

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