Fig. 7. Model for generating two peaks of nuclear Dorsal. This cartoon depicts events within the perivitelline space at two different time points for embryos laid by wild-type and grk^- females. The Spätzle cleavage reaction is hypothesized to produce an inhibitor (red), in addition to activated Spätzle (green). If processed Spätzle and the inhibitor possess different diffusion rates, the relative distribution of the two molecules would change from t₀ to t₁, giving rise to the final shape of the gradient characterized by one or two peaks of high nuclear Dorsal (blue).