Late events in T4 bacteriophage production. I. Late DNA replication is primarily exponential.

The possibility of a switch in the mechanism of T4 DNA replication, from an exponential-bidirectional mode at early stages to a nonexponential (rolling circle) mode at later stages of phage development, has been investigated. The conclusion that DNA replication does not involve such a change in mechanism for the majority of replicating molecules is based on the analysis of the clonal distribution of mutants specifically induced at late times after infection. The clonal distribution of mutants, induced by adding 5-bromodeoxyuridine to infected cells at a time when 100 phage equivalents of DNA had accumulated, fits the pattern predicted by exponential replication.