Isolation and initial characterization of the alcohol dehydrogenase gene from Drosophila affinidisjuncta

Recombinant bacteriophages containing the alcohol dehydrogenase (ADH) gene from Drosophila affinidisjuncta have been isolated by virtue of their cross-hybridization to the previously cloned ADH gene from D. melanogaster. Within the 17 kilobases of cloned DNA represented in the phage genomes, the sequences hybridizing to the D. melanogaster ADH gene lie roughly in the center. The only region of detectable hybridization to cDNA made from templates of D. affinidisjuncta larval poly(A)-containing RNA maps to the same portion of the cloned DNA. Verification that the phages carry the ADH structural gene was obtained by hybrid-selecting ADH mRNA, translating it in vitro, and immunoprecipitating the resulting ADH polypeptide. Analysis of genomic DNA suggests that the ADH gene and most flanking sequences are present only once in the haploid genome. However, 3' to the ADH gene, two separable repetitive elements are found. Both repetitive elements are probably small and poorly conserved in the genome, and neither interferes with localization of the ADH gene, by in situ hybridization, to a position near the base of the third chromosome. Analysis of ADH transcripts demonstrates that there are at least four RNAs produced by the ADH gene. Two size classes of RNA are seen at each stage of development. In addition, ADH transcripts from larvae and adults differ from one another in a reproducible manner.