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, the y gene (including the bristle enhancer), a loxP cassette containing a 755bp fragment of the Mcp boundary element of Abd-B (contains the silencer and the insulator) and a mini-w gene. The silencer of the Mcp element is oriented proximal to the y gene.