Transgenic construct used to study the Mcp boundary element. Consists of the y wing enhancer, an FRT cassette containing the w eye enhancer, the y body enhancer, a 340bp sub-fragment of the Mcp boundary element of Abd-B (contains the insulator but not the silencer), the y gene (including the bristle enhancer), a loxP cassette containing a 755bp fragment of the Mcp boundary element (contains the silencer and the insulator) and a mini-w gene.