(a) Wild-type embryos with normal somites. (B) Somite formation in embryos lacking Delta. the bracket indicates normal-looking somites where they initially form. (c) Somite formation in embryos lacking Delta, but receiving a pulse of Delta expression at the time indicated by the right-hand bracket. (D) Interactions among components of the oscillatory clock in adjacent cells. (adapted from c. Soza-ried et al., Development 141:1780–1788, 2014. With permission from the company of Biologists.) carroll SB (2006) endless Forms Most Beautiful: the New Science of evo Devo. New York: W.W. Norton & co., Inc.
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Overview of Development
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Figure Q21–3 effects of Dpp expression on wing development in Drosophila (problem 21–16). (a) Normal Dpp expression. (B) absence of Dpp expression. (c) additional anterior Dpp expression.
(D) additional posterior Dpp expression. (From M. Zecca, K. Basler  and G. Struhl, Development 121:2265–2278, 1995. With permission from the company of Biologists.) part of the wing, a large mass of wing tissue composed of normal-looking cells is produced at the site of Dpp expression (Figure Q21–3C and D). Does Dpp stimulate cell division, cell growth, or both? How can you tell?
21–17 The highly branched structures of neurons would seem to make it almost inevitable that they should make unproductive synapses with themselves, yet they manage to avoid this outcome very effectively. How is this accomplished in vertebrates?
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