Genetical variation for enzyme activity in a population of Drosophila melanogaster. III. Dominance relationships for alcohol dehydrogenase activity.

Four inbred lines, two homozygous AdhS/S and two homozygous AdhF/F, were extracted from a laboratory cage population of Drosophila melanogaster and crossed in all combinations. Directional dominance for low ADH activity was present and confined to AdhF/S heterozygotes. The remaining genetical differences between the four lines for ADH activity were due to additive genetical variation. The frequency of the AdhS allele in the population was 0-89. The observed directional dominance for low ADH activity in AdhF/S heterozygotes corresponded to the general direction of selection for ADH activity within the population.