A loxP site was inserted into intron 1 about 1 kb upstream of exon 2 and a loxP site and FRT flanked neo cassette were inserted about 0.3 kb 3' of exon 3 via homologous recombination. Flp mediated recombination removed the neo cassette. Cre mediated recombination removed exons 2 and 3. (J:212535)