A loxP site was inserted upstream of exon 6. An FRT-flanked neomycin resistance cassette with a 3' loxP site was inserted downstream of exon 7. Flp-mediated recombination removed the neomycin resistance cassette and left exons 6 and 7 floxed. Cre-mediated recombination removed exons 6 and 7. (J:197141)