An FRT site and a loxP site flanked hygromycin resistance gene and STOP cassette were inserted in intron 17 (in ENSMUST00000002487), an ENSMUST00000002487:c.1910T>A mutation was created in exon 18 (changing valine codon 637 (GTG) to aspartic acid (GAG) (p.V637E)) and an FRT site was inserted into intron 18. RT-PCR analysis indicates the mutant allele is hypomorphic, expressed at about 5-10% of the level of the wild-type allele. The mutation is the equivalent of the human c.1799T>A (p.V600E) mutation, the most common oncogenic mutation in BRAF.