Origin of the hemoglobin S gene in a northern Brazilian population: the combined effects of slave trade and internal migrations

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Abstract
We analyzed DNA polymorphisms in the b-globin gene cluster of 30 sickle cell anemia patients from Belém, the capital city of the State of Pará, in order to investigate the origin of the bS mutation. Sixty-seven percent of the bS chromosomes were Bantu type, 30% were Benin type, and 3% were Senegal type. The origin of the bS mutation in this population, estimated on the basis of bS-linked haplotypes, contradicts the historical records of direct slave trade from Africa to the northern region of Brazil. Historical records indicate a lower percentage of people from Benin. These discrepancies are probably due to domestic slave trade and later internal migrations, mainly from northeastern to northern regions. Haplotype distribution in Belém did not differ significantly from that observed in other Brazilian regions, although historical records indicate that most slaves from Atlantic West Africa, where the Senegal haplotype is prevalent, were destined for the northern region, whereas the northeast (Bahia, Pernambuco and Maranhão) was heavily supplied with slaves from Central West Africa, where the Benin haplotype predominates.