A floxed neo and stopper cassette along with the coding region of human NTRK3 from exon 6 with a polyadenylation signal was knocked into and replaced exon 6 and 7. The allele produces a fusion protein of the amino acids coded by the first 5 exons and protein tyrosine kinase domain of NTRK3. Expression of the fusion protein only occurs when the stopper cassette is removed by cre-mediated recombination. (J:130323)