3kb Ubx ABXSS enhancer fragment fused to a 3.4kb Ubx promoter fragment (3.1kb upstream sequences, 357bp mRNA leader sequence and the Ubx transcription start site) is separated from a 2kb fragment containing the complete Ubx cDNA, a 0.6kb fragment containing Ubx IRES (internal ribosome entry site) and 4kb fragment of Ecol\lacZ coding region by Hsp70 transcription termination sequences flanked by FRT sites.