Transgenic construct in which y is used as a reporter in an enhancer blocking assay; construct used to study the gypsy\su(Hw)BR insulator. Contains the y gene including the wing and body enhancers upstream of the promoter. Sequences from -144 to -69 relative to the promoter have been deleted. An FRT cassette containing eight binding sites for the Trl protein is inserted at position -893 relative to the y transcription start site. A loxP cassette containing a gypsy\su(Hw)BR insulator is inserted downstream of the y coding region, followed by a w minigene.