Developmental variation in effects of the second and third chromosomes on the activities of the glucose 6-phosphate and 6-phosphogluconate dehydrogenases in Drosophila melanogaster.

Developmental profiles of the second- and third-chromosome modifiers of the activities of glucose 6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) in Drosophila melanogaster were investigated. Third-chromosome modifiers showed very strong effects on both enzyme activities at larval, pupal, and adult stages, whereas second-chromosome effects were detected mainly at larval and adult stages. For both enzyme activities and both chromosomes, the correlation over line means between larval and pupal stages was significantly positive, but the correlation between larval or pupal stage and adult stage was not significant. This result suggests that the actions of modifiers on G6PD and 6PGD activities are influenced by the change of developmental stages. Correlation between G6PD and 6PGD activities was positive and highly significant throughout the developmental stages for both sets of chromosomes, although third-chromosome correlations were slightly higher than second-chromosome correlations. The magnitude of the correlation between G6PD and 6PGD activities does not seem to be influenced by the change of development. Diallel crosses for both sets of chromosomes indicate that the action of activity modifiers is mainly additive for both sets of chromosomes, but dominance effects were detected in some cases in adult males. Significant maternal effects were detected for the third chromosome for both enzyme activities until the pupal stage. The change of the activity modifier action after emergence of the imago and the significant correlation between G6PD and 6PGD activities were also detected for diallel progeny.