Mutagenic mechanisms in bacteriophage T4 : (bacteriophage T4, mutagenic mechanisms, heat mutagenesis)

Abstract

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.