Precursor and product in bacteriophage lambda recombination.

Analyses of the time of recombination in bacteria infected with phage lambda and in spheroplasts infected with purified phage lambda DNA indicate a preponderance of recombination occurring before replication ("early recombination") after infection with tandem dimers formed in vitro compared to linear monomer DNA and phage infections. Among the early recombinants is a large fraction of cells that produces one recombinant type exclusively. Two suggestions are discussed-that a dimer-like molecule is the precursor of the recombinant progeny molecule and that one recombinant chromosome is the frequent or exclusive product of a recombinational event.