Which factor would most directly cause a deviation from Hardy-Weinberg genotype frequencies?

Which factor would most directly cause a deviation from Hardy-Weinberg genotype frequencies?

• A. Random mating
• B. Natural selection
• C. Large population size
• D. Mutation-free environment

Answer: (B)

Hardy-Weinberg frequencies describe a stable relationship of genotypes (p^2 : 2pq : q^2) when evolution is not acting on the population. The factor that would most directly disrupt this stability is natural selection, because it changes the reproductive success of individuals based on their genotypes. If certain genotypes have higher fitness, they leave more offspring, shifting the allele frequencies in the gene pool over generations. As a result, the expected p^2 and 2pq proportions no longer apply, and genotype frequencies deviate from Hardy-Weinberg equilibrium. Random mating tends to maintain those proportions, large population size reduces random drift (which can slowly alter frequencies but not as directly as selection), and a mutation-free environment means no new alleles are introduced rather than actively changing genotype proportions.

Hardy-Weinberg frequencies describe a stable relationship of genotypes (p^2 : 2pq : q^2) when evolution is not acting on the population. The factor that would most directly disrupt this stability is natural selection, because it changes the reproductive success of individuals based on their genotypes. If certain genotypes have higher fitness, they leave more offspring, shifting the allele frequencies in the gene pool over generations. As a result, the expected p^2 and 2pq proportions no longer apply, and genotype frequencies deviate from Hardy-Weinberg equilibrium.

Random mating tends to maintain those proportions, large population size reduces random drift (which can slowly alter frequencies but not as directly as selection), and a mutation-free environment means no new alleles are introduced rather than actively changing genotype proportions.