A novel mosaic Bantu/Benin/Bantu beta s haplotype found in several African populations.

In a survey of the chromosomal backgrounds associated with the sickle cell gene in Portuguese-speaking populations from Europe and Africa, a discordance between the classical haplotype and the predicted allele at the RsaI polymorphism 5' to the beta globin gene was observed in four patients. Extensive typing of the corresponding beta s chromosomes at simple polymorphic repeat motifs revealed a novel "extended" haplotype that appeared to be a mosaic of (1) a Bantu-type DNase I hypersensitive site 2 within the beta globin gene cluster locus control region, (2) a Benin 5' subhaplotype, and (3) a Bantu 3' subhaplotype. We propose two alternative schedules for the generation of yet another chromosomal background of the sickle cell gene.