The rudimentary locus of Drosophila melanogaster

In the studies reported here, we have examined the molecular organization of the rudimentary gene of Drosophila melanogaster. rudimentary encodes a 220,000 Mr polypeptide catalyzing the first three steps in pyrimidine biosynthesis: carbamyl phosphate synthetase, aspartate transcarbamylase and dihydroorotase. We have determined the direction of transcription of the gene relative to the genetic map of the locus. The 5′ end maps to the distal end of the locus (relative to the centromere) and transcription proceeds through the domains encoding dihydroorotase, carbamyl phosphate synthetase and finally aspartate transcarbamylase. The rudimentary transcription unit spans a DNA segment of 13.2 × 10³ base-pairs and encodes a mature messenger RNA of 7.3 × 10³ base-pairs. Three intervening sequences have been identified, one of which is over 4 × 10³ base-pairs in length. Finally, we have compared the DNA sequence organization of the Drosophila rudimentary gene with the corresponding loci of yeast and hamster.