A loxP site was inserted into intron 1 and a second loxP site and an FRT site flanked neomycin resistance gene cassette downstream of a modified exon 2 where 13 codons (HPAPLSTPASKNF) had been deleted. The neo cassette was removed through subsequent flp-mediated recombination. Exon 2 was deleted through subsequent cre-mediated recombination. (J:280157)