Exon 2 was flanked by loxP sites and a FRT-flanked PGK-neomycin cassette was inserted downstream of the floxed exon 2. Flp-mediated recombination removed the selection cassette. Cre-mediated recombination deleted exon 2. Deletion of exon 2 (bp 485-732) results in a premature stop codon at amino acid 168. (J:245025)