Ultrabithorax

Ultrabithorax or Ubx is a gene found in insects, a member of the homeobox gene family, and as many homeobox genes do, functions as a transcription factor. In Drosophila melanogaster it is expressed in the third thoracic (T3) and first abdominal (A1) segments and represses wing formation. The Ubx gene regulates the decisions regarding the number of wings and legs the adult flies will have. Ubx is activated when there is a certain lack of Hunchback (hb) protein. Significant concentrations of Hunchback only exist in the anterior and posterior regions of the embryo, therefore Ubx is expressed only in middle segments. Thus, the hb gene may play an important role in the specification of the boundaries of Ubx expression.