Hardy-Weinberg Law

Genetic epidemiology aims to understand how genetic variation contributes to disease risk. To best characterize risk relationships, one must first understand how the exposure of interest is distributed within and across populations, before attempting to relate [Page 452]exposure distributions to disease distribution. For genetic exposure, this involves understanding how genetic variation arises in populations and how it is maintained within and across populations over time. The Hardy-Weinberg law describes a state of equilibrium in allele frequencies at a particular genetic locus over generations that are randomly mating. This law also describes a relationship between the allele frequencies and genotype frequencies within a population as a result of random mating.

Variation at a genetic locus can be described by noting the different ‘spellings,’ called ‘alleles,’ that exist ...