ABSTRACT
Admixture is a common type of gene flow in human populations and occurs when individuals from two or more parental populations that have been isolated for several generations form a new hybrid population. Admixed populations are common in North and Latin America, Central Asia and South Africa. Population structure (or stratification), the presence in one population of subgroups that differ in allele frequencies, can affect the results of population genetics and epidemiological studies. In this review, we analyze how population stratification and admixture affect the design and results of population genetics and association studies involving pharmacogenetic loci and drug-response related traits. Specifically, we discuss how admixture and population stratification are related to the allelic architecture of complex traits and illustrate how admixture may be a confounder in population genetics studies de signed to infer the action of natural selection. We also analyze how admixture and population stratification affect case-control association studies, and give some real and hypothetical ex amples relevant in pharmacogenetics. Finally, we briefly describe methods and software devel oped to control for the effect of population stratification: genomic control, regression, struc tured association methods and Principal Component Analysis.
