Abstract
Seven-methylguanine maybe formed in DNA as a result of treatment with MNNG. It may not be the major product of the reaction, but the mechanism may be similar to the one proposed by Henry (1950) for the reaction of MNNG with amines MNNG + amino-containing base [forward arrow] guanidino base + methyl -nitrosamine; methylnitrosamine + guanine residue [forward arrow] 7-methylguanine. Any guanidino compounds formed would probably be destroyed by acid hydrolysis. Such a reaction mechanism might explain the occurrence of 2 reactions of MNNG in Escherichia coli, only one of which is subject to repair processes.