Linkage disequilibrium at the human phosphoglucomutase 1 locus.

By considering the four common PGM1 alleles as haplotypes, that is, combinations of mutations at two polymorphic intragenic sites (1/2 and A/B), we investigated the levels of linkage disequilibrium in 142 human population samples. These groups showed considerable diversity in their disequilibrium (Drel) and heterogeneity. In all the populations the disequilibrium was found to be due to an excess of 1A and 2B haplotypes, although this direction is the opposite of that expected according to the proposed phylogeny of the system. Natural selection could be one of the major causes for such a disequilibrium direction.