In the field of reverse genetics RMCE (recombinase-mediated cassette exchange) is of increasing relevance. Based on the features of site-specific recombination processes (SSRs), the procedure permits the systematic, repeated modification of higher eukaryotic genomes by targeted integration. For RMCE, this is achieved by the clean exchange of a preexisting gene cassette for an analogous cassette carrying the "gene of interest" (GOI).