Abstract
Several pyrimidine-requiring mutants of Neurospora crassa, presumed to represent a single locus (pyr-3), have been studied in regard to the activity of aspartic carbamyl transferase of mycelia. It has been found that pyr-3 and certain other mutants yield no activity, while pyr-3a and 3b appear to contain an enzyme indistinguishable from that demonstrated in the wild type. The results suggest that the pyr-3 "locus'' is concerned with more than a single function.