title: In vitro replication of bacteriophage T7 DNA damaged by ultraviolet radiation.
abstract: The effect of ultraviolet radiation on DNA replication has been examined with an in vitro system capable of replicating intact chromosomes of T7 DNA from an exogenous template. Exposure of the template DNA to ultraviolet radiation resulted in a sharp drop in the amount of in vitro DNA synthesis. The residual replication detected when irradiated templates were used was found to proceed semiconservatively and to result in the production of pieces of duplex DNA approximately the same size as the average distance between pyrimidine dimers. It was also found that prior irradiation of the template inhibits formation of fast-sedimenting concatemer-like DNA structures normally synthesized in vitro. Hybridization studies demonstrated that the product synthesized in vitro from ultraviolet-irradiated templates includes DNA from both the left and right halves of the T7 chromosome. This may mean that after ultraviolet irradiation more than one origin of replication exists.
mesh_terms: D002501:Centrifugation, Zonal; D004260:DNA Repair / Q000528:radiation effects; D004261:DNA Replication / Q000528:radiation effects*; D005092:Exonucleases / Q000378:metabolism; D007700:Kinetics; D009693:Nucleic Acid Hybridization; D013604:T-Phages / Q000528:radiation effects*; D013698:Templates, Genetic; D014466:Ultraviolet Rays
chemical_list: D005092:Exonucleases