Geographical survey of beta S-globin gene haplotypes: evidence for an independent Asian origin of the sickle-cell mutation.

The haplotypes of 152 beta S-chromosomes were characterized in six different population groups. The chromosomes of individuals from Nigeria and from the southwest of the Arabian peninsula have the haplotype - - - - + + - + previously found in west African, Jamaican, and U.S. American blacks, whereas those from the eastern oases of Saudi Arabia and from the west and the east coast of India showed a different haplotype not found in Africa (+ + - + + + + -). These data are most consistent with an independent Asian origin of the sickle-cell mutation and provide further information about the geographic distribution of beta S-haplotypes in the Old World. The distribution of the Asian beta S-haplotype corresponds to the reported geographic distribution of a mild clinical phenotype of homozygous SS disease.