Suppressor of pyrimidine 3 mutants of Neurospora and its relation to arginine synthesis.

The basis of the mutant phenotype of the pyr 3a strain of Neurospora appears to be the arginine sensitivity of an early step in pyrimidine synthesis. The effect of a suppressor mutation which renders pyr 3a pyrimidine-independent is to reduce arginine levels in the mycelium by its effect on ornithine transcarbamylase.