Analysis of genetic variation affecting the relative activities of fast and slow ADH dimers in Drosophila melanogaster heterozygotes.

When AdhF/Adhs heterozygote homogenates are stained after electrophoresis, considerable variation is observed in the activity ration of the FF dimer to the SS dimer. Two AdhS strains showed a sharp, consistent difference when crossed to a common AdhF strain. Optical scanning and genetic analysis confirmed that this difference originates close to the Adh locus. Since the morphs varied concordantly in their activities on numerous alcohols, and since aging and heat treatment experiments failed to reveal a stability difference, it is proposed that the difference is regulatory in nature, affecting ADH synthesis and primarily cisacting. A survey of wild flies revealed additional variation in the FF/SS activity ratio. Further genetic analysis showed that the basis of this variation is not restricted to the second chromosome. Furthermore, modification of the activity ratio implies some degree of allelespecificity on the part of the modifiers.