Molecular structure of a naturally occurring alcohol dehydrogenase null activity allele in Drosophila melanogaster

An alcohol dehydrogenase null activity allele, AdhnAH52, extracted from a natural population of Drosophila melanogaster has been cloned and sequenced. Compared with the wild-type consensus sequence, the nucleotide sequence of AdhnAH52 contains eight extra bases in intron 2, adjacent to the 5' splice site. It seems likely that the extra bases result from two structural changes, with a 10-base pair insertion at the same site as a 2-base pair deletion. The insertion includes an 8-base pair duplication of an adjoining region. This structural change alters transcription to give rise to an mRNA which is longer than normal and at 10% of the wild-type level.