Transgenic construct used to study interactions between insulators. Consists of an FRT cassette containing the w eye enhancer (nucleotides -1084 to -1465 relative to the transcription start site), a 430bp gypsy\su(Hw)BR insulator, the y transcription unit, a 430bp gypsy\su(Hw)BR insulator, a mini-w gene and a loxP cassette containing a 430bp gypsy\su(Hw)BR insulator.