 Bacteria appear to use the RecF pathway of homologous recombination to repair single @-@ strand gaps in DNA . When the RecBCD pathway is inactivated by mutations and additional mutations inactivate the SbcCD and ExoI nucleases , the RecF pathway can also repair DNA double @-@ strand breaks . In the RecF pathway the RecQ helicase unwinds the DNA and the RecJ nuclease degrades the strand with a 5 ’ end , leaving the strand with the 3 ’ end intact . RecA protein binds to this strand and is either aided by the RecF , RecO , and RecR proteins or stabilized by them . The RecA nucleoprotein filament then searches for a homologous DNA and exchanges places with the identical or nearly identical strand in the homologous DNA . 
