An important motive for understanding the effects of ancestry on GWAS is preventing genomic inflation due to population stratification. Population stratification occurs when both disease prevalence and allelic frequency differences exist in the subpopulation sampled. Such stratification may lead to false positive associations of genetic signals.4 Since up to millions of markers are tested across the genome, many will show differences in allele frequency between populations and the overall distribution of test statistics will be inflated, leading to an increase in false positives, hence the term “genomic inflation.”
