FIG. 12.

Substrates used for in vitro strand exchange assays. (A) Pairing of a circular single-stranded molecule with linear duplex results in the formation of a nicked circular duplex product and a displaced linear single strand. (B) Invasion of a linear single-stranded molecule into supercoiled circular DNA results in the formation of a joint molecule with a D-loop. (C) Strand exchange between an unlabeled single-stranded oligonucleotide and labeled double-stranded oligonucleotides is detected by displacement of a labeled single-stranded oligonucleotide.