8.1 Hardy-Weinberg equilibrium and its assumptions

Hardy-Weinberg equilibrium is a key concept in population genetics. It predicts how gene frequencies remain stable across generations when no evolutionary forces are at play, providing a baseline for studying genetic changes in populations.

The model assumes specific conditions like large population size, random mating, and no mutation or selection. By comparing real populations to this ideal state, scientists can identify factors influencing genetic diversity and evolution in nature.

Hardy-Weinberg Equilibrium Fundamentals

Hardy-Weinberg equilibrium in genetics

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• Hardy-Weinberg equilibrium (HWE) describes genetic equilibrium in populations predicting gene frequencies inheritance across generations
• Mathematical model quantifies allele and genotype frequencies remain constant without evolutionary forces
• Provides null hypothesis for population genetic studies measuring evolutionary change
• Helps identify factors influencing allele frequencies (mutation, selection, migration)

Assumptions of Hardy-Weinberg equilibrium

• Large population size minimizes genetic drift effects reducing random allele frequency changes
• Random mating ensures no sexual selection or assortative mating based on genotype
• No mutation prevents new alleles introduction maintaining existing genetic variation
• No migration eliminates gene flow between populations preserving distinct genetic pools
• No natural selection means all genotypes have equal fitness without differential reproductive success

Calculations with Hardy-Weinberg equations

• Allele frequency equation: $p + q = 1$ (p and q represent two allele frequencies)
• Genotype frequency equation: $p^2 + [2pq](https://www.fiveableKeyTerm:2pq) + q^2 = 1$
  • $p^2$ = homozygous dominant frequency (AA)
  • $2pq$ = heterozygous frequency (Aa)
  • $q^2$ = homozygous recessive frequency (aa)
• Calculate allele frequencies from genotype frequencies:
  • $p = p^2 + \frac{1}{2}(2pq)$ (dominant allele frequency)
  • $q = q^2 + \frac{1}{2}(2pq)$ (recessive allele frequency)

Interpretation of Hardy-Weinberg results

• Equilibrium state shows constant allele and genotype frequencies across generations
• Deviations indicate evolutionary forces presence suggesting HWE assumption violations
• Applications include estimating recessive disorder carrier frequencies predicting future genotype frequencies
• Detects selection pressure on specific alleles by comparing observed vs expected frequencies
• Limitations acknowledge ideal conditions rarely exist in nature serving as theoretical model