Gene Networks and Natural Selection: Is There a Network Biology?

Andreas Wagner

07-09-036

Can qualitative information about large molecular networks inside cells teach us fundamentally new biology? In other words, is there a network biology (distinct from a network physics or network chemistry)? The answer to this question is important, because molecular networks are bridges between individual molecules, the lowest level of biological organization, and whole organisms. To find out whether large molecular networks can teach us new biology, we first need to answer a very basic question: Does natural selection influence the structure of biological networks, and if so, how? This question is key, because natural selection is the one central feature that distinguishes biological systems from all other, non-biological systems: Only biological systems have been shaped by natural selection, a process that acts on populations of organisms, and that requires heritable fitness differences among organisms. I will here illustrate progress in answering this question with examples from metabolic networks, transcriptional regulation networks, and protein interaction networks.