The invention relates to methods for inhibiting, cloning, modifying or labelling an endogenous DNA sequence using compositions comprising recombinases in combination with exogenous polynucleotides containing "anchoring" or "locking" sequences. The anchoring sequences serve to stabilize structures formed by the exogenous polynucleotides and the endogenous DNA. The stabilized structure thus can either serve to regulate gene transcription or replication, or can allow the endogenous sequences to be labelled or pulled out, i.e. cloned, or modified.