An Investigation of Changes in Rate of Mutagenesis by Ultraviolet Radiation During the Cell Cycle of Synchronised Bacteria

Abstract

It is now quite generally accepted that the bacterial chromosome is duplicated by the passage of a replicase enzyme from one end to the other. Replication, a specific term indicating exact duplication, always starts from the same point (origin) and continues linearly along the chromosome, each part being replicated in sequence. There is always only one point of replication involved in any one "round" of replication. (Cairns, 1963, Messelson and Stahl, 1958). Cairns’ work also showed that the rate of passage of the replication point along the chromosome was remarkably constant over a wide range of cultural conditions. In other words the reaction rate of the enzyme is not greatly affected by the growth conditions. Therefore amongst the individuals within a single culture the differences in replication rate should be negligible.