Why we need quantitative dynamic models.

Systems biology is changing the way we think about regulatory phenomena: Instead of focusing on individual components and single reactions as rate-limiting steps, we are now considering systems as a whole to understand how regulation arises from multiple interacting components. To understand the mechanisms by which interacting components become regulatory systems, we need to have a quantitative understanding of the system. At the cellular level, this means knowing the concentrations of cellular components, such as proteins, and the reaction rates for interactions between components. Mechanistic understanding of regulatory behavior will be helpful in developing predictive models of relationships between complex genotypes and variable phenotypes.