Fig. 6.

Schematic representation of a recombinase-mediated integration event. The targeting DNA is circular and contains a single recognition site (red arrow), a selectable marker and gene of interest. The accepting DNA (in genome) contains a single complimentary recognition site. The resulting integration event between the two associated recognition sites inserts the entire circular targeting DNA fragment into the genome. For the reversible recombinases this leaves an unstable configuration of two directly oriented recognition sites that can be immediately excised. Transient expression of the reversible recombinase is commonly used to trap the integrated DNA—not shown