Linkage disequilibrium of polymorphic sites in the G6PD gene in African populations and the origin of G6PD A-.

So far, four polymorphic sites are known to exist in the glucose 6-phosphate dehydrogenase (G6PD) gene of people of African origin: the mutation in G6PD A (which creates a FokI restriction enzyme site); the additional mutation in G6PD A- (which creates an NlaIII site); and two restriction fragment length polymorphisms (PvuII and PstI). We have investigated the status of these four sites in 78 men of African descent and found them to exist in linkage disequilibrium--only five of the ten haplotypes expected at least twice under a random assortment regimen were observed. The mutation of G6PD A- is found only in the presence of the PvuII and PstI sites and we therefore suggest that it has arisen only once. We propose a likely sequence for the evolution of these different mutations in the G6PD gene.