Exon 7 was replaced with a loxP site, modified exon 7 with nulceotide substitutions that result in the amino acid substitution of alanine for phenylalanine at position 397 (F397A), an FRT-flanked puro cassette and a loxP site. Flp-mediated recombination removed the puro cassette and left the modified exon floxed. (J:191578)