Genetic polymorphisms and ethnic admixture in African-derived black communities of northeastern Brazil.

Unrelated individuals from 3 relatively isolated African-derived communities in the state of Piauí, northeastern Brazil, and blood donors from Teresina (admixed population), the capital city of Piauí, were analyzed for the ESD, CA2, GC, HP, GLO1, PGM1, HB, ACP1 protein loci and for the VWF1 and VWF2 short tandem repeat (STR) loci. As expected, high frequencies of alleles considered characteristics of African populations were detected. The VWF1 allele distribution was bi-modal, whereas the VWF2 distribution was unimodal, suggesting differential action of mutation and selection factors in the 2 STRs despite their close location on the same gene. The genetic distances between the Brazilian isolates coincide with their geographic distances. The ethnic admixture estimated by a maximum-likelihood method showed African, European, and Amerindian components of 61%, 17%, and 22% for Mimbó, 72%, 12%, and 16% for Sítio Velho, and 31%, 21%, and 48% for Teresina, respectively.