Recombination of bacteriophage T7 in vivo.

Most recombination following infection with T7 was found to coincide with the time of most repid DNA synthesis, at about 20 min after infection at 30 degrees in minimal medium. Recombining DNA was investigated electron microscopically. Multiply branched DNA structures were observed after infection with T7 wild type, gene 3-, gene 6- and genes 3-, 6- phage, but not after infection with T7 gene 5- phage. Evidence is presented indicating that these structures are T7 DNA molecules in the process of recombining. The detailed structures of these recombinational intermediates suggest mechanisms by which T7 DNA initiates recombination.