Transgenic construct used in an enhancer blocking assay to study the properties of the '1A-2' su(Hw) binding region. Three copies of su(Hw) binding site 3 from the gypsy insulator plus a 78bp fragment corresponding to the 3' end of the 1A-2 region fragment have been inserted into the Yp2-lacZ reporter of P{Yp2-lacZ.FBE1.ctrl}, in between the FBE1 enhancer and the Yp2 promoter sequence.