Restriction site variation, gene duplication, and the activity of sn-glycerol-3-phosphate dehydrogenase in Drosophila melanogaster.

Restriction site variation in a 25-kb region including the sn-glycerol-3-phosphate dehydrogenase (Gpdh) locus has been assessed in 29 single female D. melanogaster lines from the Cardwell (Australia, QLD) population. The Gpdh locus was duplicated in about one-third of the lines, although the duplication was incomplete and lacked exons 1 and 2. There was no restriction site variation in the duplicated region. Three insertions were found in the gene region but only one affected GPDH activity. The lines with the duplication had higher levels of GPDH activity and protein amount than did nonduplicated lines. This effect was also observed in lines extracted from two other Australian populations. The duplication is shown to have a similar structure in each population investigated and is also present in populations from China and Africa. It is suggested that the effect of the duplication on GPDH activity, which might be due to structural factors affecting transcription at the Gpdh locus, could account for the worldwide distribution of the duplication.