[The role of vegetative and reparative DNA synthesis in correcting single-strand breaks arising upon exposure of Escherichia coli to gamma rays].

It is shown that thymine starvation stops the growth of auxotrophic cultures at the moment of combining Okazaki fragments. Amino acid starvation prevents the mitosis in cells where DNA replication has completed. Therefore, it is easy to synchronize bacterial cells and to preserve them in two different states: when the chromosome is doubled or when the cells just divided and the chromosomes is single. The postirradiation repair, studied by measuring the number of single strand breaks, is going on with the same efficiency both in wild type cells and in different repair mutants. This suggests that sister chromatide exchange does not participate in postirradiation repair, especially in that affected by the rec-system. Some data are obtained that different pools of precursors are used by the cell in case of the repair synthesis of DNA and of vegetative replication.