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THE MANY INPUTS PROBLEM. “One must also ask how a cell integrates information and instructions that come from the many different modules that monitor its internal and external environment. Neurobiology has an analogous problem, where the central nervous system integrates information from different senses and dictates the organism's behaviour.” https://www.nature.com/articles/35011540 View in LinkedIn

MULTIPLE MECHANISMS. “The melting of the surface of a solid can be induced in different ways: by changing the pressure or temperature or by adding impurities. Similarly, different organisms induce the transition between different patterns of microtubule organization that occurs during cell division by changing different members of the set of kinetic parameters that govern microtubule polymerization.” https://www.nature.com/articles/35011540 View in LinkedIn

KEY THESIS. “We have argued that most functional properties of a module are collective properties, arising from the properties of the underlying components and their interactions. Collective properties have long been studied in statistical physics and share attributes that rise above the details.” https://www.nature.com/articles/35011540 View in LinkedIn

SYSTEM TEMPLATE DESIGNS. “Modules may also be related by shared design or functional principles, even if they are not related by descent. The pheromone-detection system of budding yeast and the chemotactic machinery of bacteria use unrelated components, but both pathways achieve a sensitive response over a wide range of pheromone or chemoattractant concentrations by using reactions that specifically turn off active forms of the signalling receptors.” https://www.nature.com/articles/35011540 View in LinkedIn

RELATEDNESS. “Understanding the relatedness of modules is useful because knowledge about one member of a class can inform the study of the others. Relatedness by descent is often apparent from the homology of chemical components.” https://www.nature.com/articles/35011540 View in LinkedIn

STASIS BY NECESSITY. “But if the function of a protein is restricted to one module, and the connections of that module to other modules are through individual proteins, it will be much easier to modify, make and prune connections to other modules. This idea is supported by the analogous observation that proteins that interact with many other proteins, such as histones, actin and tubulin, have changed very little during evolution, and by theoretical arguments that proteins are difficult to evolve once they are participating in many different interactions.” https://www.nature.com/articles/35011540 View in LinkedIn

CONSTITUTIVELY CONSERVED. “If the function of a protein were to directly affect all properties of the cell, it would be hard to change that protein, because an improvement in one function would probably be offset by impairments in others.” https://www.nature.com/articles/35011540 View in LinkedIn

BIDIRECTIONAL INFORMATION. “Information flows bidirectionally between different levels of biological organization. For instance, the macroscopic signals that a cell receives from its environment can influence which genes it expresses — and thus which proteins it contains at any given time — or even the rate of mutation of its DNA, which could lead to changes in the molecular structures of the proteins. This is in contrast to physical systems where, typically, macroscopic perturbations or higher-level structures do not modify the structure of the molecular components.” https://www.nature.com/articles/35011540 View in LinkedIn