A loxP site together with an frt-flanked neomycin selection cassette was inserted in intron 1. Exon 2 contains the ATG translation initiation codon. A second loxP site was inserted distal to exon 2 in intron 2. The frt-flanked neomycin selection cassette was removed via FLP-mediated recombination. Subsequent Cre-mediated recombination in the germline resulted in the deletion of the loxP-flanked sequences including exon 2. (J:277504)