This transgenic construct is generated in vivo by using phiC31-mediated recombination to replace the attP cassette of a Mi{MIC} element insertion with an unknown phase "Trojan lexA:QFAD " cassette. The Trojan lexA:QFAD cassette consists of a splice acceptor site followed by the T2A peptide, the Ecol\lexA DNA-binding domain fused to the Ncra\QF activation domain (" lexA:QFAD ") and an Hsp70 transcription termination signal. Integration of the cassette into a Mi{MIC} insertion in a coding intron (with the same phase) of a native Drosophila gene of interest will result in the cassette behaving as a "Trojan" exon: the splice acceptor site ensures that the T2A- lexA:QFAD open reading frame is incorporated into the mRNA of the native Drosophila gene, while the T2A sequence truncates the native gene product and promotes the separate translation of the lexA:QFAD open reading frame. Thus lexA:QFAD should be expressed under the control of the regulatory sequences of the native Drosophila gene of interest in the resulting fly line.