We discuss here the functions of the Ultrabithorax domain of the bithorax complex (BX-C) of Drosophila and the role in development of the two major tran-scription units within this region. We use the term UI-trabithorax domain to refer to a region of the BX-C that is approximately 100 kb long. This region is not a single gene, but by genetic criteria, it forms a single functional unit (Lewis 1963, 1978; Bender et al. 1983; Beachy et al. 1985; Sanchez-Herrero et al. 1985). Within this domain, there are at least two transcription units. We follow Beachy et al. (1985) in referring to one of these as the Ultrabithorax (Ubx) transcription unit. This transcription unit spans the region of the chro-mosome where most mutations inactivate all functions of the Ultrabithorax domain; such mutations are de-
No takes yet. Share an insight, caveat, or question.
Akam et al. (1985) studied this question.