Replication of Bacteriophage M‐13

A mutant of bacteriophage M‐13 temperature‐sensitive in gene‐5 was isolated. The effect of this mutation on phage DNA synthesis was studied at the restrictive temperature in the presence and absence of the dnaB function which is required for early double‐strand replication. From the results obtained it is concluded that gene‐5 protein has two functions: (a) as already known it controls negatively double‐strand replication and (b) it is directly involved in progeny single‐strand synthesis.