title: The dampening of DNA replication cycles after x-irradiation or ultraviolet irradiation.
abstract: Escherichia coli strains 15T(-) (555-7) and B/r were grown in the presence of thymine-(14)C to label all DNA. The ability of these parental DNA's to undergo cycles of replication subsequent to cellular irradiation with either X-ray or ultraviolet light (UV) was followed with density labels. Exposed cells were shifted into the density medium at times which were approximately multiples of normal rounds of DNA replication. A portion of the parental DNA, replicated semiconservatively once during an initial cycle following UV or X-irradiation in E. coli, failed to replicate again within the time studied. The time course of semiconservative parental DNA replication is altered.
mesh_terms: D002247:Carbon Isotopes; D002499:Centrifugation, Density Gradient; D002586:Cesium; D004261:DNA Replication / Q000528:radiation effects*; D004269:DNA, Bacterial / Q000528:radiation effects*; D004926:Escherichia coli; D009584:Nitrogen; D011830:Radiation Effects; D011868:Radioisotopes; D013941:Thymine / Q000378:metabolism; D013997:Time Factors; D014466:Ultraviolet Rays; D014498:Uracil / Q000378:metabolism
chemical_list: D002247:Carbon Isotopes; D004269:DNA, Bacterial; D011868:Radioisotopes; D002586:Cesium; D014498:Uracil; D009584:Nitrogen; D013941:Thymine