A targeting construct was designed to insert a frt-flanked neomycin (neo) resistance cassette in opposite orientation to the gene, downstream of exon 7 of the glycine receptor, alpha 1 subunit (Glra1) gene. Nucleotide substitutions (CAG to ATC) introduced in exon 7 resulted in the amino acid mutation Q266I. Flp-mediated recombination removed the neo cassette.