Recombinant DNA molecules of bacteriophage phix174

Abstract

(Phi)X174 DNA structures containing 2 different parental genomes were detected genetically and examined by electron microscopy. These structures consisted of 2 monomeric double stranded DNA molecules linked in a figure 8 configuration. Such DNA structures were observed to be formed preferentially in host recA+ cells or recA+ cell free systems. Since the host recA+ allele is required for most (phi)X174 recombinant formation, the authors conclude that the observed figure 8 molecules are intermediates in, or end products of, a (phi)X174 recombination event. It is proposed that recombinant figure 8 DNA molecules arise as a result of 'single strand aggression', are stabilized by double strand 'branch migration' and represent a specific example of a common intermediate in genetic recombination.