Consider a situation in which an insecticide-resistant gene in the house fly Mus
ID: 261777 • Letter: C
Question
Consider a situation in which an insecticide-resistant gene in the house fly Mustica domestica, (R), is dominant to the nonresistance coding allele (r). Suppose that a new insecticide spraying program is instituted in a community to eradicate this pest. Although the insecticide chosen has a very short half-life, it is found to be extremely effective for a period of 2 weeks. From laboratory studies, you determine that 80% of flies carrying at least one R allele survive when exposed to the insecticide, but only 10% of the rr homozygotes survive the same treatment. If the initial frequency of the r allele in the population is 0.95 before the insecticide is administered, what will be its frequency one generation (2 weeks) after insecticide treatment? (assume that the relative sensitivities to the insecticide as determined in the laboratory are an accurate prediction as to the relative fitness experienced in the wild populations.)
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Explanation / Answer
The frequency of r allele is 0.95 = p
Frequency of R allele = 1 - 0.95 = 0.0 5
So genotype frequency rr homozygotes = p2 = 0.95 * 0.95 = 0.9
After 2 weeks 10% of rr types survive . Means 90% are dead so selectecs s = 0.9
So new frequency of new survivors= 0.9 * 0.9 = 0.81.