Prevalence and molecular heterogeneity of alfa+thalassemia in two tribal populations from Andhra Pradesh, India

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Abstract
We describe here the screening of a small group of apparently healthy individuals belonging to the tribal communities of Koya Dora and Konda Reddi. A remarkably high incidence of deletion and nondeletion α+ thalassemia mutants has been found with allele frequencies and distributions characteristic to each tribe. We have confirmed the strict relationship between Hb S levels and the number of α globin genes in double heterozygotes for the S gene and α thalassemia. In this population sample we did not find either heterozygous carriers of α0 thalassemia (deletion of both alpha genes in “cis”) or individuals showing hemolytic anemia due to inactivation of three α-globin genes (Hb H disease). Selection by malaria is most probably responsible for the prevalence of the various α+ thalassemia haplotypes among the two tribal populations of Andhra Pradesh.