Deletion preserving the entire P{PZ} element, which lies so that the Ecol\lacZ coding region is transcribed in the same direction as Ubx. The deletion extends from around -27kb to -61kb (coordinates of FBrf0040194), removing the Ubx origin of transcription, 3.5kb of sequences upstream of the initiation site, and 26kb downstream of it, including the positions of the first exon, the two microexons and part of the long intron. It extends to the position where the bithorax mutations map.
Ubx50.1/Ubxbx-3 flies show only a thin transformed metanotum and their halteres show a much milder transformation than that of Ubx1/Ubxbx-3 flies. UbxI.7/Ubxbx-3 flies show a stronger transformation, despite the similarity of the molecular lesions in Ubx50.1 and UbxI.7. Ubx50.1/Ubxpbx-1 and UbxI.7/Ubxpbx-1 flies show a milder phenotype in the haltere than Ubx1/Ubxpbx-1 or Ubxpbx-1/Df(3R)P9, indicating there is transvection.