6-phosphogluconate dehydrogenase in the housefly, Musca domestica L.: Evidence for inheritable 6PGD polymorphism

Two electrophoretic variants of the 6-phosphogluconate dehydrogenase (6PGD) enzyme have been found in the WHO/IN/Musca domestica/1 housefly laboratory strain. The patterns shown by Cellogel zone electrophoresis can be fully explained by the hypothesis of two codominant autosomal alleles. On this hypothesis, a specific Pgd locus has been postulated and the symbols Pgd A and Pgd B have been assigned to the two alleles causing the PGD-A and PGD-B phenotypes. The bands corresponding to the homozygous phenotypes PGD-A and PGD-B have different electrophoretic mobility and staining intensity; they can be described, respectively, as “fast-weak” and “slow-thick.” The heterozygous phenotype PGD-AB gives a three-banded pattern, indicative of a dimeric structure for this enzyme; this pattern is asymmetrical. Heterozygous flies have been found both among wild-type strains of recent colonization and among old established laboratory colonies. Most strains are Pgd B monomorphic; up to now only three strains have been Pgd A monomorphic, all of them being multimarker strains. The Pgd locus has been traced to the housefly linkage group III.