Figure 9.26. Cell specification by the Wingless/Hedgehog signaling center.

Figure 9.26

Cell specification by the Wingless/Hedgehog signaling center. (A) Bright-field photograph of wild-type Drosophila embryo, showing the position of the third abdominal segment. (B) Close-up of the dorsal area of the A3 segment, showing the different cuticular structures made by the 1°, 2°, 3°, and 4° rows of cells. (C) Model for the role of Wingless and Hedgehog. Each signal is responsible for about half the pattern. Either each signal acts in a graded manner (shown here as gradients decreasing with distance from their respective sources) to specify the fates of cells at a distance from these sources, or each signal acts locally on the neighboring cells to initiate a cascade of inductions (shown here as sequential arrows). (After Heemskerk and DiNardo 1994; photographs courtesy of the authors.)

From: The Origins of Anterior-Posterior Polarity

Cover of Developmental Biology
Developmental Biology. 6th edition.
Gilbert SF.
Sunderland (MA): Sinauer Associates; 2000.
Copyright © 2000, Sinauer Associates.

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