Pyrimidine dimers as pre-mutational lesions in Escherichia coli WP2 Hcr |
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Authors: | H -D Mennigmann |
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Institution: | (1) Arbeitsgruppe Mikrobengenetik im Fachbereich Biologie, Johann Wolfgang Goethe-Universität, Frankfurt (Main), Germany |
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Abstract: | Summary Mutation to prototrophy in E. coli WP2 Hcr- induced by far-UV radiation (F-UV) in an intermediate dose range follows dose-squared kinetics. In a comparable dose-range with near-UV radiation in the presence of acetophenone (N-UV+Acph) mutation induction follows kinetics which are linearly related to dose. The difference in response to the two types of irradiation is a more general one in that it is the same for true revertants, for suppressor mutants, and for several markers.Double-irradiation experiments together with treatment by photoreactivating light (PR) after the first irradiation (i.e. F-UVPRF-UV; N-UV+AcphPRN-UV+Acph; N-UV+AcphF-UV; N-UV+AcphPRF-UV) seem to indicate the following: a) the dose-squared kinetics for F-UV are due to the necessary co-operation of at least two types of pre-mutational lesions, only one of which is photoreversible; b) N-UV+Acph also produces these photoreversible lesions in addition to such photoreversible ones which do not require the co-operation of other types; the production of the former is not indicated by the appearance of visible mutants because the non-photoreversible type, whose co-operation is required to give rise to such mutants, is not produced. |
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