A loxP site was inserted upstream of exon 4. A cDNA encoding the remaining exons, polyadenylation sequence, CFP reporter gene, FRT site, neomycin resistance gene, loxP site and FRT site were inserted downstream and in-frame of exon 5. Flp-mediated recombination removed the section cassette leaving exons 4 and 5 floxed and the reporter gene intact. (J:221922)