Estimating European admixture in African Americans by using microsatellites and a microsatellite haplotype (CD4/Alu)

We have analyzed 10 unlinked microsatellites and a linked Alu deletion polymorphism at the CD4 locus in an African American population sample from Chicago (USA). Heterozygosity estimates at the microsatellite loci range from 0.727 ± 0.025 (D3S1358) to 0.873 ± 0.017 (D18S51), with an average of 0.794 ± 0.016. These values are comparable to or higher than those reported for Europeans, with only one exception (D3S1358). The CD4/Alu haplotypic diversity (0.887 ± 0.012) is comparable to diversity levels observed in sub-Saharan African populations and is higher than the diversity levels reported in European populations. No consistent pattern of within, between, or multi-locus deviations from Hardy-Weinberg expectations is observed, suggesting a low sub-heterogeneity within the sampled population. We have applied a maximum likelihood method and estimated the proportion of European admixture to the African American gene pool to be 0.26 ± 0.02. The narrow confidence interval indicates that allele frequency data from multiple microsatellite loci, whether analyzed independently or as haplotypes, are particularly useful for estimating genetic admixture.