A KDRT stop cassette (which also contains a single loxP site), followed by a Tag:ALFA epitope tag that is flanked by GS linkers, has been inserted into the endogenous Oamb locus in the third intracellular loop, so that it tags the K3 isoform. This results in a conditionally tagged allele; KDR recombinase can be used to excise the KDRT cassette to produce a Tag:ALFA-tagged Oamb K3 isoform.