A population of 600 horses has 70 individuals that are AA and 160 that are Aa at a locus involved in immune response.Assuming that these are the only alleles at that locus, what is the frequency of a?

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To find the frequency of allele a, first, calculate the total number of alleles for the locus in the population, which is 2 times the population size (since each individual has two alleles for each locus), giving 2 * 600 = 1200 alleles. The number of a alleles can be calculated by adding twice the number of aa individuals (but there are none explicitly mentioned, assuming AA and Aa are the only genotypes, aa is inferred) to the number of Aa individuals, since each Aa individual contributes one a allele. However, since no aa individuals are mentioned, we focus on Aa and AA. The total number of A alleles is 2*70 (from AA) + 160 (from Aa), and the remainder must be a alleles. Given 70 AA individuals contribute 0 a alleles, and 160 Aa individuals contribute 160 a alleles. If there were aa individuals, they would contribute 2 alleles each, but since the total number of individuals is accounted for with AA and Aa, we infer the rest of the alleles. The calculation for the frequency of a is then based on the total number of a alleles divided by the total number of alleles. The total number of a alleles is 1200 - (2*70 + 160) = 1200 - 300 = 900 a alleles. Therefore, the frequency of a is 900 / 1200 = 0.75.

A Population of 600 Horses Has 70 Individuals That Are