These various reasons — differences in disease-allele frequency and LD patterns, phenotypic prevalence differences, differences in effect size, and differences in rare variants — provide the scientific motivation for GWA studies in diverse populations. Some variants that act in all populations might be more easily identifiable in certain groups owing to the properties of LD and allele frequency in those groups. For some phenotypes with low prevalence in Europeans, studies might be more practical in other groups49. In addition, use of multiple populations is the only way to uncover true biological variation in underlying risk variants, including biological variation resulting from differences across populations in the occurrence of rare risk alleles.
