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. An FRT cassette containing the w eye-specific enhancer is inserted between the y wing and body enhancers. The y coding region is separated from the enhancers by a 430bp gypsy\su(Hw)BR insulator sequence (containing 12 su(Hw) protein binding sites) followed by a spacer fragment followed by a second copy of the 430bp insulator sequence. A third copy of the 430bp gypsy\su(Hw)BR insulator sequence is present downstream of the y coding region, followed by the w^+mC minigene.