EFFECTS ON ADH ACTIVITY AND DISTRIBUTION, FOLLOWING SELECTION FOR TOLERANCE TO ETHANOL IN DROSOPHILA-MELANOGASTER

Strains of Drosophila melanogaster homozygous for either the Adh(F) or the Adh(S) allele were kept on food supplemented with ethanol for 20 generations. These strains (FE and SE) were tested for tolerance to ethanol and compared with control strains (FN and SN). The E strains showed increased tolerance to ethanol both in the adult and in the juvenile life stages. In adults the increase in tolerance was not accompanied by an increase in overall ADH activity. However, there were changes in the distribution of ADH over the body parts. Flies of the FE strain possessed significantly more ADH in the abdomen, compared with FN. Another set of FN and SN populations were started both on standard food and on ethanol food with reduced yeast concentrations. After 9 months ADH activities were determined in flies from these populations which had been placed on three different media: the food the populations had been kept on, regular food and regular food supplemented with ethanol. The phenotypic effects of yeast reduction on ADH activity were considerably, but longterm genetic effects were limited

Selection against Adh null alleles in Drosophila melanogaster

Populations of Drosophila melanogaster polymorphic for an Adh null and an Adh positive allele (either Adhs or AdhF), were founded on regular food, on food supplemented with ethanol and on food suplemented with methanol. On ethanol-supplemented food Adh null was rapidly eliminated, but on regular food and on food supplemented with methanol a consistent decline in the frequency of the Adh null allele was also observed. Estimates of fitness, based on the rate of elimination of Adh nulls in the polymorphic populations were compared with estimates derived from egg-to-adult survival of F2's from crosses between homozygotes for Adh null alleles and homozygotes for Adh positive alleles. On 1-pentene-3-ol a rise in Adh null frequency was observed. Even in the absence of alcohol stress the Adh null genotypes are at a selective disadvantage which is relevant to the metabolic role of ADH and the Adh polymorphism in natural populations