Identification of a small genetic region that encodes orotate phosphoribosylatransferase and orotidylate decarboxylase in Droxophila melanogaster.

A variety of tests indicate that a small genetic region in chromosome 3R encodes at least a part of the bienzyme complex containing the last two enzymes of the pyrimidine biosynthetic pathway in Drosophila melanogaster, Complex U. Electrophoretic variants of the last pathway enzyme map to this region and both Complex U activities are proportionally reduced in flies heterozygous for specific deficiencies of the region. Complex U mutants have been isolated that lack both activities. Characteristics of these mutants are discussed relative to other pyrimidine pathway mutants known in Drosophila melanogaster and in mammals.