Question

Coloration in the peppered moth (Biston betularia) is determined by a single gene with two alleles showing complete dominance. Dark moths are homozygous dominant or heterozygous for the gene, light moths are homozygous recessive. In a sample of 100 moths, you determine that 64 of the moths are dark. According to the Hardy-Weinberg rule, the expected frequency of the dominant allele is ___.

1) 0.4
2) 0.36
3) 0.6
4) 0.64
5) cannot be determined

Answer 1

According to the Hardy-Weinberg principle and the given information, the expected frequency of the dominant allele for dark coloration in the peppered moth sample is 0.4.

Step-by-step explanation:

The question pertains to the frequency of the dominant allele in the population of peppered moths (Biston betularia). As given, we have 64 dark-colored moths out of 100. According to the Hardy-Weinberg principle, the population is in genetic equilibrium, so the allele frequencies can be calculated using the formula p^2 + 2pq + q^2 = 1, where p is the frequency of the dominant allele, q is the frequency of the recessive allele, and p^2 represents the frequency of the homozygous dominant genotype, 2pq represents the heterozygous genotype, and q^2 represents the homozygous recessive genotype.

To find the expected frequency of the dominant allele (p), we start by determining q. If light moths represent the homozygous recessive genotype (q^2), then q can be found by taking the square root of the fraction of light-colored moths (q^2). In this sample, there are 36 light-colored moths because the rest of the 100 are dark. So q^2 = 36/100 = 0.36 and q = √0.36 = 0.6. Since p + q = 1, p must be 0.4 (1 - q).

Therefore, the expected frequency of the dominant allele (p) according to the Hardy-Weinberg rule is 0.4 (option 1).