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説明
Summary Since various kinds of potential mutagens will increase to a tremendous extent, we need not only simple and sensitive mutagen test systems but also classification of mutagenicities. An Escherichia coli test system is evaluated from these standpoints. Phenotypic reversion to prototrophy of a strain with an amber nonsense marker is sensitive enough to detect residual mutagenicity in ethylene-oxide-sterilized plastic petri dishes on the marked. A biological classification of induced mutageneses is proposed; it is based not on chemical specificities of mutagens but on the involved biological factors, i.e., DNA repair systems. Differential reversibilities by 8 popular mutagens of a set of 4 strains with the same amber nonsense marker but different DNA repair capacities (wild type, uvrA-, polA-, recA-) lead to the following classification. (I) mutagenesis by recA-dependent misrepair of (i) excisable DNA damage [UV, 4-nitroquinoline- i -oxide (4NQO)], (ii) unexcisable DNA damage [X-rays, methyl methanesulfonate (MMS)], or (iii) excision-repair-induced DNA damage [mitomycin C (MMC)]; and (II) recA-independent misreplication mutagenesis [N-methyl-N'-nitro-N-nitrosoguanidine (NG), ethyl methanesulfonate (EMS), hydroxylamine (HA)]. The model that the recA-independent mutagenesis is, at least partly, due to mutagen-induced damage to the replication machinery is supported by induction of mutation in phage λ after infection of NG-pretreated host bacteria of either a recA+ or recA- strain.
収録刊行物
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- Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis
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Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 26 235-241, 1974-08-01
Elsevier BV