NETWORKS

The recent explosion of genomic data has inspired a renewed interest in how groups of genes work together to create observable phenotypes. Studies of genetic networks have shown a surprising degree of robustness to variation, regardless of whether the variation comes from a change within or outside of the network. One explanation for this pattern is that evolution has acted to create genetic networks that are robust to mutational defects at single genes within the network. Using a combination of mathematical and computational models, Stephen R. Proulx and Patrick C. Phillips investigate the evolution of genetic networks in response to a variety of genetic and environmental perturbations. The models show that natural selection for robustness will only be as strong as the cost of disrupting the network. Because the risk of mutational damage is limited by the mutation rate, these results imply that robustness to mutation will play only a small part in the evolution of genetic networks. Environmental perturbations, on the other hand, can affect large fractions of a population and are thus more likely to play a significant role in genetic network evolution.