A loxP site resides 5' of exon 2, and a FRT-flanked neomycin selection cassette followed by a second loxP site lies 3' of exon 4. Subsequent flp-mediated recombination removed the neo cassette. Crossing mice with this allele to Cre-expressing mice leads to excision of exons 2 through 4 in tissues of their progeny. (J:153876)