A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2? a. 0.7 b. 0.49 c. 0.42 d. 0.21

Verified step by step guidance

1. Understand the Hardy-Weinberg principle, which states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.
2. Identify the given allele frequencies: frequency of A1 (p) = 0.7 and frequency of A2 (q) = 1 - p = 0.3.
3. Use the Hardy-Weinberg equation for heterozygotes, which is 2pq, to find the proportion of the population that carries both A1 and A2 alleles.
4. Calculate 2pq = 2 * 0.7 * 0.3 = 0.42.
5. The proportion of flies that carry both A1 and A2 alleles is 0.42, which corresponds to answer choice c.

Key Concepts

Hardy-Weinberg Equilibrium

The Hardy-Weinberg equilibrium is a principle that describes the genetic variation in a population that is not evolving. It states that allele and genotype frequencies will remain constant from generation to generation in the absence of evolutionary influences. This model assumes no mutation, migration, selection, or genetic drift, providing a baseline to compare real populations against.

Allele Frequencies

Allele frequency refers to how often a particular allele appears in a population compared to other alleles for the same gene. In this case, the frequency of allele A1 is 0.7, meaning 70% of the gametes carry this allele. The frequency of allele A2 can be calculated as 1 - frequency of A1, which is 0.3, or 30%.

Genotype Frequencies

Genotype frequency is the proportion of different genotypes in a population. Under Hardy-Weinberg equilibrium, the frequencies of the genotypes can be calculated using the allele frequencies. For two alleles A1 and A2, the expected genotype frequencies are p^2 (homozygous A1), 2pq (heterozygous A1A2), and q^2 (homozygous A2), where p and q are the frequencies of A1 and A2, respectively.