Genetical variation for enzyme activity in a population of Drosophila melanogaster. II. Aspects of the inheritance of alcohol dehydrogenase activity in Adhs/s flies.

Two inbred lines of Drosophila melanogaster extracted from a laboratory cage population and homozygous for the AdhS allele of alcohol dehydrogenase (Adh) showed almost a twofold difference in specific activity. Analysis of generations derived from these lines showed that the genetic variation in ADH activity was controlled by additive gene action. There was no evidence of directional dominance or of non-allelic interactions. Although the Adh structural gene is on the second chromosome there was a significant effect of the X chromosome, indicating the action of modifying genes.