Abstract
Riboflavin afforded the mutagenic effect on transforming deoxyribonucleic acid (DNA) from Bacillus subtilis through photodynamic action, and upon the addition of adenine to the irradiation mixture the mutagenic effect was greatly accelerated. Most of auxotrophic mutants among the transformants required tryptophan or tyrosine. The mutation was closely correlated with the photodynamic inactivation of the DNA, and it was suggested that both the inactivation and the mutation were caused by the selective photodegradation of guanine residues in DNA.
