Spontaneous mutagenesis

The tautomerisation of the purine bases adenine and guanine and of the pyrimidine bases thymine, cytosine, and uracil has important implications in molecular biology, and the occurrence of rare tautomeric forms of these bases has been suggested as a possible cause of spontaneous mutagenesis (Lowdin, 1965 Pullman and Pullman, 1971 Kwiatowski and Pullman, 1975). Three of the most likely tautomers for cytosine are shown in [87]—[89], together with the less likely imino forms [90] and [91] (Scanlan and Hillier,... 

Many plasmids are known to possess three properties (1) increased resistance to the bactericidal effects of UV and chemical mutagens, (2) increased spontaneous mutagenesis, and (3) increased susceptibility to UV and chemically induced mutagenesis. Some plasmids possess all three properties others may possess just one, for example, increased susceptibility to mutagenesis (review Mortelmans and Dousman, 1986). Often the profile of activity depends on the DNA repair status of the host cell (Pinney, 1980). Plasmid pKMIOl carries DNA repair genes and has been widely used in strains used in bacterial mutagenicity tests. 

Mutagenesis is the process of producing a mutation. If it occurs in nature without the action of a known mutagen, it is called spontaneous mutagenesis and the resulting mutations are spontaneous mutations. If a mutagen is used, the process is called induced mutagenesis. 

Substitution Insertion Deletion Duplication 1 bp 1 to several bp 1 to several bp 1 to several bp Spontaneous mutagenesis Rephcation infidelities Gene silencing Gene expression Cryptic gene activation Altered protein specificities... 

Lenne-Samuel, N., Wagner, J., Etienne, H., and Fuchs, R. P. (2002). The processivity factor /3 controls DNA polymerase IV traffic during spontaneous mutagenesis and translesion synthesis in vivo. EMBO Rep. 3, 45-49. 

Goncharova El, Rossman TG (1994) A role for metallothionein and zinc in spontaneous mutagenesis. Cancer Res (in press)... 

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