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Evolutionary Theory

Author(s): Tadzia GrandPré, PhD, Nancy Moreno, PhD, and Lisa Marie Meffert, PhD

Deviations from the Hardy-Weinberg Equilibrium

Hardy-Weinberg calculations identify the allelic and genotypic frequencies expected from generation to generation, when a population is in Hardy-Weinberg equilibrium. For a population to reach and maintain this equilibrium, it must meet criteria (e.g. random mating patterns, no mutation, no selection) that are essentially unattainable outside of a laboratory setting. Thus, evolution occurs when natural populations deviate from Hardy-Weinberg equilibrium, causing shifts from the expected allelic and genotypic distributions. The major mechanisms that drive these shifts are selection, mutation, migration, genetic drift, and non-random mating.