Nucleotide Sequence of the Origin for Bacteriophage M13 DNA Replication

M13, fd, and fl are three very closely related filamentous bacteriophages that belong to the Ff group (for review, see Ray 1977). These bacteriophages contain a single strand of DNA that replicates in three stages. Initially, the infecting viral strand is converted to duplex or replicative-form DNA (SS~RF) (Ray et al. 1966; Pratt and Erdahl 1968), which subsequently replicates to form a pool of RF DNA molecules. In the final stage of Ff DNA replication, the pool of RF DNA molecules erves as precursor for the asym-metric synthesis of progeny single-stranded DNA (RF~SS) (Ray 1969; Lin and Pratt 1972). The origin of complementary-strand synthesis and that of viral-strand synthesis have been localized. The synthesis of the complementary strand in the in vitro