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. A gypsy\su(Hw)BR insulator has been inserted between the y enhancers and the promoter, at position -343 relative to the y transcription start site. A w minigene is present downstream of the y coding region.