Hardy-Weinberg Assumptions in Population Genetics

Hardy-Weinberg Assumptions

• Dominance alone does not change allele frequencies over generations
• Large populations are assumed to maintain genetic equilibrium
• Random mating is assumed, with no inbreeding (e.g. Carlos 2nd of Spain, a product of inbreeding in Spanish royalty, breaks this assumption)
• Diploid organisms are assumed, with no mutation, selection, or migration

Assumptions Violations

• Assortative mating (e.g. humans mating for height, as seen in Van Kleef-Boltons' study) breaks the random mating assumption
• Small population size can lead to genetic drift, causing alleles to rise or fall in frequency, or even be lost from the population, resulting in a loss of diversity
• Mutation can change allele frequencies
• Migration (e.g. domestic cat genes into Scottish wildcat populations, introducing domestic cat alleles into most wildcats) can also alter allele frequencies

Natural Selection and Hardy-Weinberg Equilibrium

• If genotype frequencies do not agree with Hardy-Weinberg assumptions, it may indicate natural selection
• No selection is observed in cases like Sickle cell anaemia, where heterozygotes have an advantage, and recessive homozygotes often die young due to the lack of the genotype
• If p² + 2pq + q² ≠ 1, the population is not at Hardy-Weinberg equilibrium

Hardy-Weinberg Assumptions

• Dominance alone does not change allele frequencies over generations
• Large populations are assumed to maintain genetic equilibrium
• Random mating is assumed, with no inbreeding (e.g. Carlos 2nd of Spain, a product of inbreeding in Spanish royalty, breaks this assumption)
• Diploid organisms are assumed, with no mutation, selection, or migration

Assumptions Violations

• Assortative mating (e.g. humans mating for height, as seen in Van Kleef-Boltons' study) breaks the random mating assumption
• Small population size can lead to genetic drift, causing alleles to rise or fall in frequency, or even be lost from the population, resulting in a loss of diversity
• Mutation can change allele frequencies
• Migration (e.g. domestic cat genes into Scottish wildcat populations, introducing domestic cat alleles into most wildcats) can also alter allele frequencies

Natural Selection and Hardy-Weinberg Equilibrium

• If genotype frequencies do not agree with Hardy-Weinberg assumptions, it may indicate natural selection
• No selection is observed in cases like Sickle cell anaemia, where heterozygotes have an advantage, and recessive homozygotes often die young due to the lack of the genotype
• If p² + 2pq + q² ≠ 1, the population is not at Hardy-Weinberg equilibrium