HW Equilibrium - Background

Hardy-Weinberg equilibrium describes the null model of evolution.

For a population to be in Hardy-Weinberg equilibrium, five conditions must be met:

1. No Genetic Drift (Infinite Population Size)
2. No Migration (No Gene Flow)
3. No Mutation
4. No Selection (No Differential Mortality)
5. Random Mating (No Differential Reproduction)

If all five of these conditions are met, the allelic and genotypic frequencies will remain the same from generation to generation.

If there is a significant difference between the known (observed) and calculated (from allelic frequencies) genotypic frequencies, then the population is not in H-W Equilibrium. This result implies that one of the five conditions is not met for the locus in question. A Chi-Square test is typically used to determine whether or not there is significance between the known and calculated genotypic frequencies.