Abstract
Restriction fragments that contain the origin of DNA replication of bacteriophage f1 were inserted in vitro into circular f1 DNA molecules to form genomes that contain 2 origins. This DNA was used to transfect Escherichia coli. Analyses of the DNA of the progeny phage indicated that 1 origin and the DNA segment located between the 2 origins in the infecting DNA molecules were eliminated. This result is interpreted to mean that the nucleotide sequence of the origin for plus (viral)-strand synthesis also serves as the signal for the termination of DNA synthesis.