Practice question

Mutation introduces new alleles, genetic drift randomly fluctuates frequencies by finite sampling, and migration introduces alleles via movement between populations, all potentially altering p and q over time. Random mating alone without selection does not change allele frequencies; it only rearranges existing alleles into genotype proportions p squared, two pq, q squared predicted by binomial expansion. By random union of gametes, allele frequencies remain constant across generations, providing Hardy-Weinberg null expectation. Thus random mating influences genotype frequencies while leaving underlying allele frequencies untouched under idealized conditions.