Transgenic construct used to study insulator function. Consists of a loxP cassette containing a 430bp gypsy\su(Hw)BR insulator sequence, a w minigene with a deletion from -279 to -32bp relative to the w transcription start site, an FRT cassette containing a 430bp gypsy\su(Hw)BR insulator and a y reporter gene. The loxP cassette is located at nucleotide -116 relative to the w promoter.