Abstract
The spontaneous mutation rate for the glutamic acid gene was 0.8 per 104 conidia, and that for the citrulline gene was 0.005 per 104 conidia. Mutation rates at both loci increased with increasing X-ray dosage. The present work does not obviate the shortcomings of past mutation-rate experiments, but it provides a methodology that may prove useful in subsequent studies of gene stability in Neurospora.