Andrea LOETTGERS

Departement de Philosophie

Université de Genève

Varieties of Noise (Monday April 27th, 11h30-12h30)

Almost intuitively we associate with noise a nuisance. However, this association began to dissolve with the emergence of synthetic biology, in which noise gained a functional component. In the context of synthetic biology, noise is understood as stochastic uctuations, due, for example, to the relatively small number of molecules in a cell. But stochastic uctuations have been a topic in biology before, for example, in the release of neurotransmitters at the synaptic gap, which cause uctuations in signaling transfer. What changes associated with the emergence of synthetic biology triggered the development of a functional meaning of noise? One of the most important innovations of synthetic biology, is the development of a specific new modeling approach. Mathematical models now function as blueprints and are transferred into material models, which consist of biological components. The materiality of the synthetic model makes possible a direct manipulation on biological entities, without being forced to deal with the complexity of model organisms. Synthetic models are hybrid systems located in-between mathematical models and model organisms. How is this materiality and this location between mathematical models and model organisms linked to an transformation in the understanding of noise? Synthetic models are constructed entities "epistemic artifacts" used in the production of new knowledge about biological systems. In the construction of these epistemic artifacts, assumptions are made concerning the structure and organization of biological systems. Following the tradition of Francois Jacob, Jacque Monod, Brian Goodwin and Arthur Winfree, who also dealt in their research with organizational principles in biological systems, synthetic biologists make use of engineering concepts in the design of their synthetic systems. Well known example are the Toggle Switch of James Collins and the Repressilator of Michael Elowitz and Stanislas Leibler. As was the case before in molecular biology, engineering concepts now entered synthetic biology via the drawing of analogies between biology and engineering. Philosophers of science have shown that analogical reasoning provides scientists with a powerful cognitive strategy to transfer concepts, formal structures, and methods from one discipline to another (see e.g. Mary Hesse, Nancy Nersessian, Daniela Bailer-Jones, Derdre Gentner). With the possibility of actually building gene regulatory networks, the process of analogical reasoning becomes a material one. The materiality of the synthetic models has important epistemic implications. It allows for the probing of how far the analogy between engineered and biological systems can be extended and where it reaches limitations. The extension of the concept of noise is a result of the probing and manipulation of synthetic systems with their analogy driven design which became material.