Isolation and Structural Analysis of the extra sex combs Gene of Drosophila

During Drosophila embryogenesis, the developmental pathways of the abdominal, thoracic, and the posterior head segments are determined by genes of the bithorax complex (BX-C) (Lewis 1978; Sánchez-Herrero et al. 1985) and Antennapedia complex (ANT-C) (Kaufman et al. 1980; Lewis et al. 1980a,b). Whereas each of these genes determines the identity of only a single or a few neighboring compartments, other genes affect the identity of all or most segments (Lewis 1978; Struhl 1981; Duncan 1982; Duncan and Lewis 1982; Ingham 1983, 1984; G. Jürgens, pers. comm.). Genes of this second type appear to play a central role in the overall regulation of the activity of the gene products of the BX-C and ANT-C genes, as well as of genes determining the head segments. Therefore, to understand the regulatory circuits active during early development, it seems important to identify the molecular targets of these genes and gene products. One of these...