Testing HWE

We can easily test for deviation from Hardy-Weinberg equilibrium using a chi-square. This can arise from,

1. Marital assortment: "like marrying like".
2. Inbreeding
3. Population stratification: multiple subgroups are present within the population, each of which mates only within its own group (homogamy), and the allele frequencies are different within each subgroup (Wahlund effect). Mating within each group is random.
4. Admixture: the breakdown of any of the former processes will lead to deviations until equilibrium is reached.
5. Decreased viability of a particular genotype: individuals carrying a deleterious genotype die early (or in utero).