Transgenic construct which contains two divergently transcribed reporters: a w^+C marker and a lacZ reporter; a fragment containing two copies of the proximal enhancer from the twi promoter region and a fragment from the iab-5 cis regulatory region of Abd-B have been inserted between the two divergent promoters. A test fragment from Wnt2 has been inserted in between the 2xPE and iab-5 regulatory sequences. lacZ and white will be expressed in the 2xPE and iab-5 domains if the test fragment does not have insulation activity.