What is the Hardy-Weinberg equation and what do p and q represent?

What is the Hardy-Weinberg equation and what do p and q represent?

• A. p + q = 1; p^2 + 2pq + q^2 = 1; p and q are allele frequencies; p^2, 2pq, q^2 are genotype frequencies.
• B. p^2 + 2pq + q^2 = 1; p and q are genotype frequencies.
• C. p + q = 1; p^2 + 2pq + q^2 = 1; p and q are genotype frequencies.
• D. p + q = 2; p^2 + q^2 = 1.

Answer: (A)

In a population that's not evolving, the frequencies of the two alleles, p and q, must add up to 1, since they account for all copies of that gene. If you look at the combinations of these alleles in offspring, squaring the sum (p + q) gives the expected genotype frequencies: p^2 for individuals with two copies of the first allele, 2pq for heterozygotes, and q^2 for individuals with two copies of the second allele. Because p + q = 1, those genotype frequencies also add up to 1. So p and q are allele frequencies, and p^2, 2pq, q^2 are genotype frequencies. This matches the correct interpretation of the Hardy-Weinberg setup.

In a population that's not evolving, the frequencies of the two alleles, p and q, must add up to 1, since they account for all copies of that gene. If you look at the combinations of these alleles in offspring, squaring the sum (p + q) gives the expected genotype frequencies: p^2 for individuals with two copies of the first allele, 2pq for heterozygotes, and q^2 for individuals with two copies of the second allele. Because p + q = 1, those genotype frequencies also add up to 1. So p and q are allele frequencies, and p^2, 2pq, q^2 are genotype frequencies. This matches the correct interpretation of the Hardy-Weinberg setup.