Transgenic construct used to study interactions between boundary elements from the bithorax complex. Consists of 10 UAS sites, an FRT cassette containing a 858bp Fab-7 element (in forward orientation relative to the w gene), the y transcription unit, a loxP cassette containing a 340bp Mcp element (in forward orientation relative to the w gene) and a w minigene. The UAS sites are at -893bp relative to the y transcription start site, and at a distance of almost 5kb relative to the w transcription start site.