# Populations GEnetics?

4. The 25 founders of an isolated island population included one albino (aa).

Assuming the remaining 24 founders were homozygous AA, what would be the

frequency of the heterozygotes after three generations of random mating? If the

population had meanwhile increased to 625 individuals, approximately how many

would you expect to be homozygous for albinism? How much would the

accidental death of one albino in such a population alter the gene frequencies?

5. In one study of a heavily polluted area near Birmingham, England, Kettlewell

(1956) observed a frequency of 87 percent melanic morphs (phenotypes) of the

moth Biston betularia. Assume that melanism is caused by a dominant allele, and

calculate the frequency of the dominant allele leading to melanism in this

population and the frequency of the melanics that are expected to be

heterozygous under conditions of Hardy-Weinberg equilibrium.

Relevance

4. The frequency of albinos,aa, is 1/25 or 0.04, so the frequency of the a allele is sqrt(0.04) or 0.2 =q. Therefore, the frequency of p is1-0.2 or 0.8 = p. The frequency of heterozygotes is 2pq from the H-W equation: 2(0.8)(0.2) = 0.32. Since the population is in equilibrium, the frequencies will stay the same for those 3 generations. At a population size of N=625, the frequency of albinos is still 0.04 or 25 individuals.

The death of 1 albino removes 2 a alleles; I'll leave the calculations to you.

5. There are 87% melanic morphs (call them D_), which means there are 13% light moths; the frequency of dd, then, is 0.13. The frequency of d is sqrt(0.13) = 0.361 = q. Therefore, the frequency of D = 1-0.361 = 0.639 = p.

The frequency of heterozygotes is 2pq or 2(0.361)(0.639) = approximately 0.461

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• i'd pass with D. organic decision should not be random. those with genes that improve their odds of survival and duplicate are systematically chosen for and those with negative characteristics are chosen adverse to. Eg. A hairless polar undergo does not do so properly contained in the arctic.

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