Figure 2.

 Regulatory specficity in the Scr–ftz interval of the ANT-C. Embryos were hybridized with either a dioxigenin-labeled Scr or ftz antisense RNA probe and visualized via histochemical staining. The embryos are undergoing the rapid phase of germ-band elongation (4–5 hr postfertilization) and are oriented with anterior to the left and dorsal up. Scr is expressed within the primordia of parasegment 2 (PS 2), which gives rise to regions of the labial and prothoracic segments. ftz is expressed in a series of pair–rule stripes. The diagram below the embryos shows the location of the AE1 enhancer within the Scr–ftz interval. AE1 specifically interacts with the ftz promoter to maintain the seven-stripe pattern. It does not activate the linked Scr gene.