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