A loxP-flanked exon 3 with a polyA sequence, FRT-flanked neomycin selection cassette, and a modified exon 3 encoding the C-terminus of mouse Gnrhr fused in-frame with the intracellular cytosolic tail (Ctail) of the chicken GNRHR replaced the endogenous exon 3. The neomycin selection cassette was removed via flp-mediated recombination. Cre-mediated recombination removed the floxed exon 3 leaving an exon 3 composed of the mouse C-terminus fused with the chicken intracellular cytosolic trail. (J:324870)