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(a) Calculate the relative fitnesses of females having these genotypes.

(b) If a population of fruit flies has an initial frequency of ADHF equal to .2, what will be the frequency in the next generation when alcohol is present?

(a) Fitness is the relative reproductive output of a genotype and is calculated by dividing the average number of offspring produced by that genotype by the mean number of offspring produced by the most prolific genotype. The fitnesses of the three ADH genotypes therefore are:

Although each population has a total of 100 breeding adults, the effective population size of population B is much smaller because it has a greater disparity between the numbers of males and females.

(b) The effective population size determines the amount of genetic drift that will occur. Because the effective population size of B is much smaller than that of population A, we can predict that population B will undergo more genetic drift, leading to greater changes in allelic frequency, greater loss of genetic variation, and greater genetic divergence from other populations. 4. Alcohol is a common substance in rotting fruit, where fruit fly larvae grow and develop; larvae use the enzyme alcohol dehydrogenase (ADH) to detoxify the effects of this alcohol. In some fruit-fly populations, two alleles are present at the locus than encodes ADH: ADHF, which encodes a form of the enzyme that migrates rapidly (fast) on an electrophoretic gel; and ADH5, which encodes a form of the enzyme that migrates slowly on an electrophoretic gel. Female fruit flies with different ADH genotypes produce the following numbers of offspring when alcohol is present:

Genotype

ADHFADHF ADHFADHS ADHSADHS

Mean number of offspring

0 0

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