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Fig. 7 | BMC Evolutionary Biology

Fig. 7

From: Why and how genetic canalization evolves in gene regulatory networks

Fig. 7

How canalization evolves. We identified two main processes involved in the evolution of canalization: a shrinkage of mutational target and b redundancy of regulatory information. The blue gene is the output of the network (the only one having an effect on fitness). Square boxes represent regulatory sites (in this example, all interactions are enhancing gene expression), rectangles represent genes. The box colors match the color of the corresponding regulatory gene, and their size is proportional to the effect of the regulation (two small boxes have the same effect as one big box). The green gene (not shown) is assumed to be expressed constitutively. Black arrows indicate locations (either regulatory sites or gene sequences) which will be canalized (mutations in these sequences have no effect on fitness). In a, the replacement of a weak orange site by a weak green site excludes the orange gene from the “useful” network. In b the new strong orange regulator is redundant and can compensate the loss of both sensitivity or expression of the purple gene

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