A targeting vector was designed to insert a single loxP site followed by a frt-flanked neomycin resistance (neo) cassette upstream of exon 5, and a second loxP site downstream of exon 6. Exons 5 and 6 encode a flavin adenine dinucleotide binding site and the N-terminal portion of the amine oxidase domain, both required for enzymatic activity. FLPe-mediated recombination removed the selection cassette. (J:201572)