Analysis of the transcription unit adjacent to the 3'-end of the dopa decarboxylase gene in Drosophila melanogaster.

Using strand specific RNA probes, we have ascertained that the transcription unit immediately downstream of the dopa decarboxylase (DDC) gene in Drosophila, is oriented in the opposite direction to DDC. The 3'-termini of these two transcription units lie within 550 bp of one another, and the mature transcripts actually may overlap. We show here that the inclusion of part of the 3'-flanking transcript on a genomic DNA clone originally assumed to include just DDC, accounts for most of the hybridization seen in our previous Northern analysis of very early embryonic RNA. Thus, while DDC-specific transcripts are detectable in the early embryonic stages, they are much less prevalent than we have previously reported.