Hardy-Weinberg equilibrium requires which of the following absent in the population?

• A. Mutation, nonrandom mating, migration
• B. Random mating only
• C. Mutation and selection
• D. No mutation, random mating, no migration, very large population size, and no selection

Answer: (D)

Hardy-Weinberg equilibrium describes a population where allele and genotype frequencies remain constant across generations when no evolutionary forces are at work. For this to happen, five conditions must hold: no mutations introducing or changing alleles, random mating with respect to the gene, no migration bringing in or removing alleles, a very large population to prevent genetic drift, and no natural selection favoring one allele over another. When all of these are true, allele frequencies (p and q) stay the same and genotype frequencies follow p^2, 2pq, q^2.

The option stating no mutation, random mating, no migration, a very large population, and no selection matches these requirements exactly, so it is the best choice. Other options fail because they include factors like mutation, nonrandom mating, migration, or selection, any of which can alter allele frequencies and violate equilibrium.