WORKSHOP SUMMARY: DNA STRAND BREAK REPAIR IN EUKARYOTES

Abstract

Ionizing radiations and a number of chemical agents produce strand breaks in DNA. One reason is the tendency for strand breaking agents to produce many types of lesions in DNA in addition to strand breaks. It is well established that many such strand breaks are rapidly repaired. The major reason is the relatively small number of strand breaks in cellular DNA after exposures to strand-breaking agents for which the ability of cells to form colonies has dropped substantially. In the measurement of DNA single-strand breaks, the most used method is that of alkaline gradient sedimentation. The numbers of breaks can be determined with reasonable accuracy when exposure to strand breaking agents, for example, X-rays has reduced the single-strand molecular weight to about 5 × 10 8 daltons or less. Reliable measurements do not seem possible by alkaline sedimentation for smaller numbers of breaks( larger single-strand DNA).