Showing papers on "Lambda phage published in 1968"
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TL;DR: DNA synthesis of early sus (suppressor sensitive) mutants of phage λ in su − cells was studied by the density-gradient centrifugation method and it was found that superinfection of a heteroimmune lysogen by a sus P mutant fails to elicit the function required for replication of the superinfecting phage genome.
132 citations
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121 citations
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63 citations
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TL;DR: Results provide a firm evidence that the defect of the uvrD mutant is different from other Her- mutants and in the process of repair synthesis, and may provide a more direct method to study the mechanisms of UV reactivation than the plaque assay.
Abstract: SummaryIt has been shown that linear DNA molecules of phage λ are converted to the twisted circular structure (species I) by covalent closure of the both strands at the cohesive ends after infection to the immune bacteria and that the twisted circular molecules are transformed to the circular form (species II) by a single-strand break in one of the strands of their DNA. This system offers a very sensitive method to study on the strand breaks or their repair. For characterization of the defects of ultraviolet sensitive strains, the structural changes of ultraviolet irradiated λ DNA in these strains were studied.Ultraviolet irradiation to λ phage greatly reduced the extent of conversion of the molecules to the species I in the uvrD mutant while the irradiation showed little effect on the conversion in the uvrA, B and C mutants. When infected bacteria carrying species I molecules were irradiated, the species I molecules in the uvrD mutant were disrupted while most of the molecules in the uvrA, B and C mutants kept the structure. These results indicate that in the irradiated λ DNA strand breaks are rarely introduced or, if introduced, repaired rapidly in the uvrA, B and C mutants and they are introduced in the uvrD mutant leading to the degradation of the DNA. These results provide a firm evidence that the defect of the uvrD mutant is different from other Her- mutants and in the process of repair synthesis.Ultraviolet irradiation to the uvrD mutants promote the formation of the species I molecules from the infected irradiated λ-DNA.Such effect was not observed with the uvrA mutant. Since the uvrD mutant has UV reactivation capacity and the uvrA mutant has not, the above phenomenon is probably caused by UV reactivation and may provide a more direct method to study the mechanisms of UV reactivation than the plaque assay.
53 citations
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TL;DR: The prediction from sedimentation properties that one intracellular form of lambda DNA is a twisted, closed-circular molecule has been confirmed by observation in the electron microscope, and a new consequence of DNA circularity is evident from these studies.
49 citations
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42 citations
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38 citations
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9 citations
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TL;DR: It was found that the sus P lambda mutants were the least efficient in degrading species I phage DNA and it is suggested that the P cistron may be involved in directing the synthesis of a phage specific endonuclease which attacks the twisted, circular, covalent configuration of phageDNA.
3 citations