FIGURE 2: Rad51-catalysed strand exchange reaction. Circular ssDNA is pre-incubated with Rad51 to allow Rad51 binding to DNA without competition. RPA is then added to the reaction to remove secondary DNA structures. Nucleated Rad51 can replace RPA and form a functional continuous nucleofilament. When linear dsDNA is added Rad51 can catalyse the strand exchange between the double-stranded donor and the circular ssDNA.