Nucleotide sequence evidence of the unicentric origin of the β^C mutation in Africa

The origin of the β C mutation was studied by characterizing nucleotide sequence polymorphisms on β C chromosomes of patients from various African countries. In the majority of cases, the β C mutation was found in linkage disequilibrium with a single chromosomal structure as defined by classical RFLP haplotypes, intergenic nucleotide sequence polymorphisms immediately upstream of the β-globin gene, and intragenic β-globin gene polymorphisms (frameworks). In addition, three atypical variant chromosomes carrying the β C mutation were observed, and are most probably explained either by a meiotic recombination (two cases) or by one nucleotide substitution occurring in an unstable array of tandemly repeated sequences (one case). These data demonstrate the unicentric origin of the β C mutation in central West Africa, with subsequent mutational modification in a small number of instances. The data also supports gene flow of the β C chromosome from subsaharan Africa to North Africa. © 1991 Springer-Verlag.