Abstract
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.
