Mutagenic mechanisms in bacteriophage T4 : (bacteriophage T4, mutagenic mechanisms, heat mutagenesis)
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Mutagenic mechanisms can be divided into two categories, those dependent upon specific base mispairing (generating base pair substitutions and frameshift mutations) and those dependent upon misrepair (perhaps as a result of untemplated DNA synthesis).The genetic characteristics of bacteriophage T4 and of certain of its rII mutants permit specific mutational pathways to be identified. Once a target base pair is identified, it becomes possible to deduce the specific target base. This mode of analysis has been applied to heat mutagenesis, which occurs by two distinct mechanisms . G:C [rightwards arrow] A:T transitions are generated by the deamination of cytosine . G:C [rightwards arrow] Py:Pu transversions are generated by the conversion of guanine to a pyrimidine analogue, probably by N-glycosidic bond migration. Endogenous heat mutagenesis may present a serious challenge to the human genome.