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 w^+mC minigene, flanked on each side by a 430bp gypsy\su(Hw)BR insulator sequence (containing 12 su(Hw) protein binding sites) has been inserted at position -893 relative to the y transcription start site, with the direction of w transcription oriented opposite to that of y.