Transgenic construct used in an enhancer-blocking assay. A gypsy fragment (nucleotides 647-1077, which includes 12 su(Hw) binding sites) has been inserted into the Yp1-Yp2 intergenic region present in P{CR2}, in between the divergently transcribed Adh and lacZ reporters (fragment is inserted at position -90 relative to the Yp1 promoter).