Effect of Sodium Azide on Photodynamic Induction of Genetic Changes in Yeast

In view of the increasing attention to 1O2 (1Δg) participation in the photodynamic action, different types of genetic changes in Saccharomyces cerevisiae by acridine orange sensitization were compared with respect to the response to N3‐, a well known quencher of 1O2. The induction of mitotic crossing over with respect to ade 2 locus and mitotic gene conversion at trp 5 locus were suppressed by the addition of N3‐ suggesting the involvement of 1O2 as a major intermediate. However, the induction of reverse mutation at ilv 1 was only slightly suppressed. These results may indicate that there are two types of photodynamic DNA damage; one is produced via 1O2 and the other via non‐1O2 reaction pathway which lead to mitotic gene conversion and mitotic crossing over, and to mutation, respectively.