Abstract
Using Hayflick's model, ultraviolet (UV) induced unscheduled DNA synthesis was compared in cells at a low, middle and high population doubling level (PDL). Concomitant DNA replication was prevented by arresting all cultures in the G 1 phase by lowering the serum concentration. After UV-irradiation cells at a high PDL incorporated 1.5–2 times more [ 3H] thymidine into DNA than cells at a low and middle PDL. These findings seem to indicate that the repair capacity of cells at a high PDL is more than those of cells at low and middle PDL. Alternatively, the higher incorporation might be explained by a difference in the pool sizes of precursors of cells at different PDL. These possibilities were examined by adding fluorodeoxyuridine to the system to reduce de novo synthesis of deoxythymidine triphosphate (dTTP), and measuring the pool size of dTTP and the specific activity of [ 3H] dTTP in cells at different PDL. The results indicated that the increased incorporation in fact reflects increased unscheduled DNA synthesis in cells at a high PDL.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
