Prize Talk: Max Delbruck Prize in Biological PhysicsGeometry and Genetics

The application of quantitative methods to biological problems faces the choice of how much detail to include and the generality of the conclusions. The middle ground entails some use phenomenology, a well-regarded approach in physics. A sampling of examples will be presented from my work in developmental biology, to give a flavor of what is possible. The phenomenon of canalization is a license to develop models that are quantitative and dynamic yet do not begin from an enumeration of the relevant genes. Modern mathematics (ie post 1960), under the rubric of 'dynamical systems', has many similarities to experimental embryology and allows the enumeration of categories of dynamical behaviors. Examples from stem cell differentiation will illustrate how systems with a few variables can be fit to cell state transitions and the self-organizing capacity of cell aggregates, 'organoids'. Geometric arguments alone suffice to enumerate a short list of 'typical' parameter spaces, i.e., phase diagrams for how states transform into each other. Phenomenology of the sort envisioned is essential to bridge the scales from the cell, to tissue, to embryo, by breaking the system into blocks that can be separately parameterized.