Induction of c-mutations in extracellular phage lambda by gamma-rays |
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Authors: | S. E. Bresler V. L. Kalinin I. N. Suslova |
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Affiliation: | (1) Leningrad Institute of Nuclear Physics, 188350 Gatchina, Leningard District, U.S.S.R. |
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Abstract: | Summary Mutagenic action of 60Co -rays on extracellular phages red+ and red1 13 after irradiation in 4% nutrient broth in the absence or in the presence of 0.1 M cysteamine or in dried samples was studied. The yield of c mutations was almost independent of the repair genotype of the host cells (uvrA6, polA1, recA13, lexA102, uvrE502, uvrD3 or xthA9), of the phage Red function and of the conditions of -irradiation and was 1·10-12 per base pair and 1 rad. When the SOS-repair system of the host cells was induced by moderate UV irradiation, the yield of c-mutations was drastically enhanced in phage irradiated in broth, but not in phage irradiated in the dried state. These data allow us to suppose that the direct action of -rays induces, in phage DNA, premutational lesions that are fixed into mutations by replication. On the other hand after -irradiation in broth, when indirect radiation effects are only partially suppressed, about 85% of premutational lesions are converted into mutations by means of the inducible, errorprone SOS-repair system. |
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