Using recombination mediated cassette exchange (RMCE) a modified BAC containing 9 serially ligated transposons was introduced into the RMCE ready locus Hprttm1Brd. The modified BAC vector also included a loxP site, a neo cassette, FRT sites flanking the serially ligated transposons, 2 poly A signals and a lox511 site. Each transposon consisted of sleeping beauty inverted terminal repeats flanking a splice acceptor site, a variable cDNA, and a poly A signal. The cDNAs used in each transposon were, in order from 5' to 3'; a human MYC cDNA, a human KRAS2B isoform specific cDNA containing a G12D mutation, a human KRAS2A isoform specific cDNA containing a G12D mutation, GFP, lacZ, a human BRAF cDNA, a human KRAS2A isoform specific cDNA, a human BRAF cDNA containing a V600E mutation, and a human KRAS2B isoform specific cDNA. (J:166283)