Two loxP sequences flanking conserved non-coding sequence 1 (CNS1 (Rr123)), in intron 1, as well as an FRT site flanked neomycin resistance gene cassette were inserted by homologous recombination. In addition, an EGFP cassette was inserted in-frame into the first coding exon. The selection cassette and the CNS were removed by flp- and cre-mediated recombination. (J:156942)