Mutations induced by 60Co gamma-irradiation in double-stranded M13 bacteriophage DNA in nitrous-oxide saturated solutions are characterized by a high specificity

Irradiation of double-stranded M13 mp10 DNA in a diluted aqueous solution under N2O leads to a very specific mutation spectrum. Fifteen of 28 mutations induced in a 144 base pair (bp) target are C/G to G/C transversions, the other five bp substitutions are C/G to A/T transversions. Six mutations were single bp deletions, one is a large deletion of 180 bp and one is a 10 bp duplication which is probably from spontaneous origin. The mutations are not randomly distributed throughout the 144 bp mutation target but concentrated around two sites. The differences and similarities with the radiation-induced mutation spectrum previously obtained under oxygen are discussed.