Crossing over between regions of limited homology in Escherichia coli. RecA-dependent and RecA-independent pathways.

We have developed an assay for intermolecular crossing over between circular plasmids carrying variable amounts of homology. Screens of Escherichia coli mutants demonstrated that known recombination functions can only partially account for the observed recombination. Recombination rates increased three to four orders of magnitude as homology rose from 25 to 411 bp.