Biological and chemical effects of mustard gas in yeast.

Mustard gas induces inactivation and mutation in yeast. Both effects are dose-proportional, indicating single-hit events. Induction of both effects is influenced by the cell's capacity for DNA dark-repair, whereby the probability of reversion is highest in repair-proficient cells. Binding of mustard gas to cells and probably to DNA is independent of DNA-repair systems. The number of inter-strand cross-links, as determined by assaying for renaturability of alkalidenatured DNA, increases in a dose-proportional manner. At 37% survival an excision-deficient strain contains 55 inter-strand cross-links. Chromatographic analysis yields several alkylation products of DNA. Their relative frequencies resemble the values reported for E. coli and bacteriophage T7.