Transgenic construct in which y and w are used as reporters in an enhancer blocking assay; construct used to study the gypsy\su(Hw)BR insulator. Contains the y^+t7.7 minigene, which includes partially overlapping body and wing enhancers located, respectively, at positions -1266 to -1963 and -1808 to -2873 relative to the transcription start site. A 430bp gypsy\su(Hw)BR insulator sequence (containing 12 su(Hw) protein binding sites) has been inserted together with a spacer fragment between the y enhancers and the y coding region, so that the insulator fragment is 2.4kb upstream of the y transcription start site. The w^+mC minigene is present downstream of the y coding region.