Hardy-Weinberg Equilibrium

Definition

Hardy-Weinberg Equilibrium is a fundamental principle in population genetics that describes the condition under which allele and genotype frequencies remain constant from generation to generation in a population, provided that certain assumptions are met. It serves as a baseline for studying evolutionary processes, and deviations from this equilibrium can indicate the effects of factors like selection, mutation, migration, and genetic drift. Understanding this concept helps explain how genetic variation is maintained or altered within populations.

5 Must Know Facts For Your Next Test

1. Hardy-Weinberg Equilibrium assumes no mutation, migration, selection, or genetic drift, and that mating is random.
2. In a population at Hardy-Weinberg Equilibrium, the allele frequencies can be used to calculate expected genotype frequencies using the formula: $$p^2 + 2pq + q^2 = 1$$ where p and q are the frequencies of two alleles.
3. If any of the assumptions of Hardy-Weinberg Equilibrium are violated, the population may experience changes in allele frequencies over time.
4. Hardy-Weinberg principles are commonly used as a null model to compare actual genetic data from populations and assess evolutionary forces at play.
5. The equilibrium is named after mathematicians G. H. Hardy and Wilhelm Weinberg, who independently formulated the principle in 1908.

Review Questions

• How does Hardy-Weinberg Equilibrium serve as a benchmark for evaluating the effects of positive and negative selection on allele frequencies?
  • Hardy-Weinberg Equilibrium provides a baseline expectation for allele frequencies in a non-evolving population. When positive or negative selection occurs, it disturbs this equilibrium by favoring certain alleles over others. For instance, positive selection increases the frequency of advantageous alleles, while negative selection reduces the frequency of deleterious alleles. By comparing observed allele frequencies against those predicted by Hardy-Weinberg Equilibrium, researchers can assess the impact of selection on genetic variation.
• Discuss how population structure can influence Hardy-Weinberg Equilibrium and lead to deviations in observed allele frequencies.
  • Population structure refers to the presence of subpopulations within a larger population that have different allele frequencies due to factors like geographic separation or social behavior. This structure can disrupt Hardy-Weinberg Equilibrium by introducing assortative mating or limiting gene flow between subpopulations. As a result, allele frequencies may differ significantly between groups, leading to deviations from expected frequencies calculated under Hardy-Weinberg principles. Understanding this influence helps clarify how admixture and genetic diversity arise within structured populations.
• Evaluate the implications of deviations from Hardy-Weinberg Equilibrium in relation to population genetics and evolutionary biology.
  • Deviations from Hardy-Weinberg Equilibrium indicate that evolutionary forces such as natural selection, genetic drift, mutation, or migration are acting on a population. These changes can have profound implications for understanding how populations adapt over time, maintain genetic diversity, or face extinction. By analyzing these deviations, researchers can infer important insights about historical population dynamics and predict future evolutionary trends. Such evaluations are crucial for conservation efforts and managing biodiversity effectively.

Related terms

Allele Frequency: The relative frequency of an allele at a genetic locus in a population, expressed as a proportion or percentage.

Genetic Drift: A mechanism of evolution that involves random changes in allele frequencies in a population, which can lead to significant changes over time, especially in small populations.

Natural Selection: The process by which certain traits increase in frequency within a population due to those traits providing a survival or reproductive advantage.