Mi{Trojan-GAL4.1} represents a transgenic construct generated in vivo by using phiC31:int-mediated recombination to replace the attP cassette of a Mi{MIC} element insertion with an intron phase 1 'Trojan GAL4' cassette. The donor for the Trojan GAL4 cassette can be any one of the following: a microinjected plasmid (pBS-KS-attB2-SA(1)-T2A-Gal4-Hsp70) or an insertion of a transgenic construct (P{lox(Trojan-GAL4)x3} or P{loxP(Trojan-GAL4.1)}). The Trojan GAL4 cassette consists of a splice acceptor site followed by the T2A peptide, the GAL4 coding sequence 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-GAL4 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 GAL4 open reading frame. Thus GAL4 should be expressed under the control of the regulatory sequences of the native Drosophila gene of interest in the resulting Trojan-MiMIC GAL4 driver line.