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. Author manuscript; available in PMC: 2010 Apr 12.
Published in final edited form as: Curr Opin Genet Dev. 2009 Oct 29;19(6):571–578. doi: 10.1016/j.gde.2009.09.007

Figure 3. Different mechanisms of evolution in transcriptional regulatory systems at distinct time scales.

Figure 3

An ancestral module (genes A–E) controlled by one TF (blue ovoid) and site (green box) is shown on top. A. At shorter time scales (~20 million years), loss and gain of the cis-regulatory site allows fine-tuning of module membership. B. Gain of a new control through a new cis-regulatory element (blue box) and TF (red ovoid) can lead to elaboration. Subsequent loss of one of the elements from some of the module’s genes can lead to splitting (bottom), at longer time scales (~150 million years). C,D. Wholesale re-wiring is observed at longer times (~200->300 million years), by full switching of the targets of the regulatory system (trans factor and cis elements) from one set of genes (A–E, red) to another (K–O, yellow).