Homeotic selector gene complexes
Antennapedia and Ultrabithorax

    Left: The labial (lab) and Deformed (Dfd) gene control the formation of head segments. The Sex comb reduced (Scr) and Antennapedia (Antp) genes specify the identity of the first two thoracic egments. The remaining gene in the complex, Proboscipedia (Pb), may not act during embryogenesis, but may be required to maintain the differentiated state in adult. In Antp mutants, the labial palps are transformed into legs.

    Right: The Ultrabithorax (Ubx) gene controls structures in the posterior compartment of T2 (wings) and structures in T3 (halteres). The two other genes, abdominalA (abdA) and AbdominalB (AbdB), specify the segmental identifies of the eight abdominal segments (A1-A8). In Ubx mutants, halteres are transformed into wings.


Text after Klug & Cummings ©2007 by Steven M. Carr