Evidence for retrotranscription of protein-coding genes in the Drosophila subobscura genome

Evidence is provided for the presence of retrosequences (also named retroposons) arising from Adh in the Drosophila subobscura genome. Restriction analysis and primary structure of two different retrosequence-containing clones, S812 and S135, are reported. The fact that these retrosequences lack introns and a recognizable promoter strongly supports their retrotranscriptional origin. Adjacent to the two retrosequences analyzed, a middle repetitive DNA element has been found which bears no clear similarity to any sequence reported to date in the GenBank/EMBL Data Library. A comparative analysis of these retrosequences with the functional Adh gene of D. subobscura is presented. In addition, a model concerning the origin, functionality, and propagation of these genome elements is discussed.