Transgenic construct used to study interactions between insulators and promoters. Consists of 10 UAS sites, an FRT cassette containing the Abd-B promoter targeting sequences (Abd-B-PTS) and Fab-8 insulator (nucleotides 63683 to 64582 in clone DS07696) in the forward orientation, the y coding region, a loxP cassette containing the Abd-B-PTS-Fab-8 fragment in the reverse orientation and the mini-w gene.