Molecular analysis of a spontaneous insertion mutation near the alcohol dehydrogenase gene of Drosophila melanogaster.

The structural integrity of the Adh gene in several isogenic lines of Drosophila melanogaster was tested by Southern blot analysis using a 4.75 kilobase (kb) genomic clone of Alcohol dehydrogenase (Adh) as a probe. One line, RI22, III, showed evidence of a spontaneous insertion mutation 5' to the adult enhancer in an area previously indicated as a putative larval enhancer region. The inserted allele was present at an approximate frequency of 50% in relation to the uninserted wildtype allele. Isogenic lines were constructed of both homozygous mutant and wildtype flies, allowing the comparison of a spontaneous insertion mutant allele and it's direct wildtype ancestral allele. The inserted sequence is a 296 basepair (bp) truncated jockey retroposable element. The sequence and distribution of the element as well as it's proximity to the Adh gene are discussed.