The following elements were inserted into the mouse Fzd3 (frizzled homolog 3 (Drosophila)) locus via homologous recombination: a loxP site in intron 2, a 3HA (hemagglutinin) epitope in the coding region between the cysteine-rich domain and the first transmembrane domain, a loxP site in intron 3, and an Frt-flanked PGK-neo cassette. The neomycin cassette was removed by germline Flp-mediated recombination. (J:101977, J:207894)