Final answer:
In a population at Hardy-Weinberg equilibrium, the proportion of individuals showing the dominant trait remains constant over time, provided that no evolutionary forces such as natural selection, mutation, genetic drift, or migration are affecting allele frequencies.
Step-by-step explanation:
In a population that is in Hardy-Weinberg equilibrium, the proportion of individuals showing the dominant trait at a given locus remains constant over time. This concept stems from the Hardy-Weinberg principle, which states that allele frequencies in a population will remain stable from one generation to the next, provided there is no natural selection, mutation, genetic drift, migration, or nonrandom mating affecting them. The presence of these factors can disrupt the equilibrium, leading to changes in allele frequencies within the population.
For example, if a hypothetical population has a gene with two alleles, A (dominant) and a (recessive), and the population is in Hardy-Weinberg equilibrium, the frequencies of these alleles will stay the same from one generation to the next unless disrupted by evolutionary forces. This means that the proportion of individuals displaying the dominant trait (associated with allele A) will not increase or decrease as long as the conditions for Hardy-Weinberg equilibrium are met.