Transgenic construct used to investigate the possible role of z protein in long-range interactions between enhancers and promoters. An FRT cassette containing the w eye enhancer (-1180 to -1450bp relative to the transcription start site), followed by ~1000bp w upstream sequence (from -1180 to -165bp relative to the endogenous w transcription start site), is fused upstream of the w+mC mini-gene.