A Simple Gene with a Complex Pattern of Transcription: The Alcohol Dehydrogenase Gene of Drosophila melanogaster

Excerpt

The dimeric enzyme alcohol dehydrogenase (ADH) is coded for by a single, relatively simple, gene in Drosophila melanogaster. Natural populations of this species are commonly polymorphic for two different classes of Adh allele that code for electrophoretically distinguishable enzymes. This polymorphism allowed Grell et al. (1965) to map the responsible genetic locus and, subsequently, to induce mutations that lacked ADH activity (Grell et al. 1968). These mutant Adh alleles revealed the function of the gene; flies lacking ADH activity were found to be very susceptible to ethanol. Moderate (e.g., 6%) concentrations of ethanol that are quite harmless to wild-type D. melanogaster kill genotypes that are homozygous for Adh-null mutations (Vigue and Sofer 1976). Subsequently Sofer and his colleagues (Sofer and Hatkoff 1972; O'Donnell et al. 1975) were able to use chemical selection to recover flies with functional Adh alleles from those that are mutant, since ADH will oxidize relatively nontoxic...