Genetical variation for enzyme activity in a population of Drosophila melanogaster. vi. molecular variation in the control of alcohol dehydrogenase (ADH) activity

Summary

Four characters, ADH activity at 25°, immunologically determined ADH protein level, total protein and body weight were measured upon 72 hour old adult female and male Drosophila melanogaster from 16 highly inbred lines, derived from the laboratory population, “Texas” (established 1966). The highest levels of ADH activity and ADH protein level were observed in the 2 lines homozygous for the Adh^F allele. Amongst the 14 Adh^S/S lines variation for ADH protein level was associated with genetical variation for ADH activity (r̂ = 0·6). The genetical association between ADH activity or ADH protein level and either body weight or total protein in the 16 inbred lines was not statistically significant. A study of ADH activity, ADH protein and total protein in 8 lines representing all homozygous combinations of chromosomes I, II and III and derived from two inbred Adh^S/S lines, chosen for their respective high and low ADH activities, showed that ADH activity was considerably modified by a post-translational event controlled from chromosome III. Total protein was controlled by different chromosomal effects from those controlling ADH activity. Michaelis constants for crude fly extracts of the two Adh^F/F and the above two Adh^S/S lines showed clear differences in affinity for isopropanol.