Transgene used in an enhancer blocking assay. Contains an 8kb fragment encoding the entire y gene including the wing and body enhancers. An FRT cassette containing the w eye-specific enhancer (Ee) (-1084 to -1465 bp upstream of the w transcriptional start) has been inserted between the y wing and body enhancers, at -1868 relative to the y transcription start site. A 690bp fragment containing the Mcp boundary element from the bithorax complex has been inserted at -893 relative to the y transcription start site. The y sequence is followed by 1. a loxP cassette containing a 430bp gypsy\su(Hw)BR insulator sequence, and 2. a w minigene.