An FRT-flanked neomycin resistance cassette with a 5' loxP site was inserted upstream of exon 2. An additional loxP site was inserted downstream of exon 3. Flp-mediated recombination removed the slection cassette and left exons 2 and 3 floxed. Cre-mediated recombination removed exons 2 and 3. (J:235786)