Variations in the expression of the gene Pgd due to the effect of chromosomal rearrangements in Drosophila melanogaster.

The effects of chromosomal rearrangements on the expression of the gene Pgd coding for 6-phosphogluconate dehydrogenase (PGD) was studied in D. melanogaster. Of 21 chromosomal rearrangements examined, 2 produced complete loss of PGD activity, 10 markedly decreased it, 3 slightly increased it, and 6 had no appreciable effect. The effect of some rearrangements can be restricted to the larval stage. The results of histochemical staining and the quantitative analysis of the electrophoretic PGD patterns allowed us to identify chromosomal rearrangements whose inhibition of PGD activity was due to mosaic expression of the Pgd gene. The rearrangements whose effects are variegated represented 50% of those decreasing the expression of the marker gene or about 25% of those we considered.