Five independently acting enhancers of the eve gene producing seven stripes of eve expression in the early embryo. (a) The eve gene and its upstream and downstream enhancers, any one of which can activate eve expression if bound by the correct combination of transcription factors. Numbers 1 through 7 indicate the stripe(s) activated by each enhancer (see Figure 21-14). (b) The binding sites in the stripe 2 enhancer for the Bicoid and Hunchback activators and the Krüppel and Giant repressors. (c) Changes in concentration of the four transcription factors along the length of the embryo in the region that expresses eve stripe 2.