A loxP and FRT-flanked neomycin selection cassette were inserted upstream of exon 16 and a second loxP site was inserted downstream of exon 19. Flp-mediated recombination removed the neomycin selection cassette. Cre-mediated recombination deleted exons 16-19, fusing exons 15 and 20 to create an out-of-frame transcript. (J:232437)