Sequence encoding a T2A-GAL4(DBD)::Zip- split driver component followed by a loxP-flanked Disc\RFP3xP3.cUa marker has been inserted into a coding exon within endogenous Krn. This results in a presumed loss of function of the target gene and allows expression of GAL4(DBD)::Zip- under the control of endogenous regulatory sequences.