NITROUS ACID MUTATION OF TRANSFORMING DNA: CONSIDERATION OF MODE OF ACTION.

Apparently nitrous acid produces genetic alterations, expressed as antibiotic-resistant markers, directly on heat-denatured transforming DNA of Haemophilus influenzae, rather than producing DNA which acts as a non-specific mutagen. The markers which arise as a result of treatment with nitrous acid behave similarly to naturally occurring antibiotic markers. In addition, data comparing the expression and replication of induced markers to natural markers suggest that the nitrous acid-induced markers express and multiply in the same fashion as do "normal" markers. Therefore, mutations which require additional time to produce a functional DNA by a base-pair substitution, or by replication of the introduced DNA, are not responsible for the mutants observed.