Transduction versus "Conjuduction": Evidence for Multiple Roles for Exonuclease V in Genetic Recombination in Escherichia coli

The analysis of genetic recombination mechanisms has proceeded slowly in particular because of the difficulty of detecting in vivo recombination intermediates, as opposed to fully viable recombinant progeny of a cross which can be scored genetically. We have been developing and using a technique (Birge and Low 1974; Lloyd and Low 1976) in which genetic crosses can be analyzed in two stages: (1) the early stage leading to the production of recombination intermediates that can be transcribed, and (2) the late stage leading to the maturation of these transcribable intermediates into finished replicatable recombinant chromosomes. The stages in this scheme are outlined in Figure 1. The parental recombining molecules on the left are meant to represent any of a large number of possible configurations of DNA, brought together by any of a variety of gene transfer modes (Low and Porter 1978). The central box in Figure 1 shows that the...