SummaryDNA samples from 60 Mapuche Indians, representing 39 maternal lineages, were genetically characterized for (I) nucleotide sequences of the mtDNA control region; (2) presence or absence of a nine base duplication in mtDNA region V; (3) HLA loci DRBI and DQAI; (4) variation at three nuclear genes with short tandem repeats; and (5) variation at the polymorphic marker D2S44. The genetic profile of the Mapuche population was compared to other Amerinds and to worldwide populations.Two highly polymorphic portions of the mtDNA control region, comprising 650 nucleotides, were amplified by the polymerase chain reaction (PCR) and directly sequenced. The 39 maternal lineages were defined by two or three generation families identified by the Mapuches. These 39 lineages included 19 different mtDNA sequences that could be grouped into four classes. The same classes of sequences appear in other Amerinds from North, Central, and South American populations separated by thousands of miles, suggesting that the origin of the mtDNA patterns predates the migration to the Americas. The mtDNA sequence similarity between Amerind populations suggests that the migration throughout the Americas occurred rapidly relative to the mtDNA mutation rate.

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Testing the fit of population data to Hardy-Weinberg proportions is crucial in the validation of many current approaches in population genetic studies. In this paper, we tested fit to Hardy-Weinberg proportions using exact approaches for both the overall and individual heterozygote genotype data of four HLA Class II loci: DRB1, DQA1, DQB1, and DPB1, from 26 human populations. Eighty of 99 overall tests fit the Hardy-Weinberg expectation (73% for DRB1, 89% for DQA1, 81% for DQB1 and 81% for DPB1). Deviations from Hardy-Weinberg proportions were both locus and group specific. Although we could not rule out other mechanisms at work, the individual test results indicated that the departure was possibly partly due to recent admixture. Evidence for selection and other sources of deviation are also discussed.

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Molecular genetic techniques were used to type nine loci in the HLA class II region in 241 unrelated African-Americans from New York City (NYC). Several effects attributable to recent genetic admixture were evident: the number of distinct class II alleles and haplotypes was larger in the African-Americans than in people of African or European origin, the allele frequencies were more consistently even, and linkage disequilibrium was present across the entire class II region. The African-American DRB1 allele frequencies almost always fell between frequencies among samples from northern Europe and the Gambia, two possible founding populations. The exceptions are attributed to the contribution of other genetically dissimilar African groups to the African-American gene pool. DRB1 allele frequencies (specifically DRB1*1501) and some haplotypes of DRB1-DPB1 were different in our NYC and the 11th International Histocompatibility Workshop (IHW) samples of African-Americans. The high level of allele and haplotype diversity found in African-Americans has important implications for the construction of pools of unrelated potential donors for tissue transplantation.