In the Trpv6 gene, a loxP site was inserted upstream of a modified exon 13 in which nucleotide substitutions (GAT to GCC) result in the amino acid substitution of aspartic acid with alanine at position 581 (p.D581A). An FRT site flanked neomycin resistance gene cassette with a 3' loxP site was inserted downstream of the last exon (15) into intron 16 of the Ephb6 gene on the opposite strand. Subsequent flp-mediated recombination removed the neo cassette, leaving a conditional-ready allele with exons 13-15 of Trpv6, as well as exons 17 and 18 of Ephb6, floxed.