Transgenic construct used to study potential chromatin barrier activity within the irradiation-responsive enhancer region (IRER) located upstream of rpr. An FRT cassette containing a 395bp sub-fragment of the IRER has been inserted into the pBT3 vector. The resulting construct is comprised of a 661bp fragment containing the UbxPRE, a loxP cassette containing the gypsy su(Hw)-binding region, the FRT cassette containing the IRER sub-fragment and a Disc\RFP3xP3.PB marker.