Irradiation of DNA in a cellular environment leads to many types of DNA damage, resulting from various effects of gamma-radiation. One of these effects is the formation of water-derived radicals (e.g., . @entity2145 radicals), which are formed in the vicinity of DNA (indirect effect). To study the influence of the indirect effect on gamma-radiation-induced mutations, a newly constructed plasmid, containing the @entity11524 gene as a target gene, was irradiated with 60Co gamma-radiation in aqueous solution, in the presence of @entity26 . Under these circumstances, only . @entity2145 radicals will be responsible for the induced mutations. Sequence analysis of the gamma-radiation-induced mutations showed that 96% of all mutations were base pair substitutions, 87% of which occurred in the @entity11524 gene, the others are formed in the lac operator part. All gamma-radiation-induced mutations in the @entity11524 gene occurred exclusively on G:C base pairs, and no mutations at A:T base pairs could be detected. In the spontaneous mutation spectrum, 83% of all mutations were base pair substitutions, 35% of which occurred in the @entity11524 gene and 48% in the lac operator part. Base pair substitutions on G:C base pairs were very similar in the gamma-radiation-induced and in the spontaneous mutation spectrum, implying a high contribution of . @entity2145 radicals to spontaneous mutagenesis. A:T to G:C transitions accounted for 10% of all spontaneous base pair substitutions in the @entity11524 gene and are probably the result of effects, other than just . @entity2145 radicals. It can be concluded that . @entity2145 radicals are an important source for mutations at G:C base pairs. In this paper, the extracellular gamma-radiation-induced mutation spectrum is also compared to the previously obtained, intracellular gamma-radiation-induced mutation spectrum of the @entity11524 gene. Comparison shows some differences, such as relative high amounts of mutations at A:T base pairs, G:C to T:A transversions and frameshift mutations in the intracellular gamma-radiation-induced mutation spectrum, as compared to the extracellular gamma-radiation-induced mutation spectrum. Since the extracellular gamma-radiation-induced mutation spectrum shows that . @entity2145 radicals are mainly responsible for base pair substitutions on G:C base pairs, mutations at A:T base pairs in the intracellular gamma-radiation-induced mutation spectrum are apparently the result of additional or other factors.

Mutation spectrum in the XXXX gene, induced by gamma-radiation in aqueous solution under oxic conditions.

@entity11524 :: ('7035', 'Gene') :: ['lacI'] @entity26 :: ('MESH:D010100', 'Chemical') :: ['oxygen'] @entity2145 :: ('MESH:C031356', 'Chemical') :: ['OH']
@entity11524 :: (7035,Gene) :: ['lacI']
