ABSTRACT
Population genetics is about allele frequencies. It is concerned to examine the factors that determine allele frequencies, how they may differ between populations or between subsets of individuals within a population, and how they may change or be changed. All population substructure leads to assortative mating, violating the random mating requirement of the Hardy-Weinberg relationship. A suitable panel of ancestry informative markers would comprise markers distributed across the genome that show large allele frequency differences between populations, negligible linkage disequilibrium with one another, and a Hardy-Weinberg distribution within each of the tested populations. Societies differ in the range of consanguineous marriages that they permit. The risk of serious abnormality in a baby is roughly doubled when the parents are first cousins—but that only reduces the chance of a normal baby from 98% to 96%. The Hardy–Weinberg distribution describes the relationship between allele frequencies and genotype frequencies in an undisturbed, random-mating population.
