Some of Nature’s most beautiful phenomena can be seen in the development of an embryo, from a single cell to a complete organism. In fruit flies, this takes just one day. More surprisingly, one can read a blueprint for the body plan of the fully developed organism by measuring the concentrations of just a handful of different molecules even three hours after the egg has been laid. This blueprint is extraordinarily precise, providing enough information for each cell to “know” its absolute position in the embryo with ~1% accuracy. This becomes even more surprising when we learn that the relevant molecules are present at very low concentrations, so one would expect these signals to be very noisy. Understanding how the embryo extracts enough information from such limited signals raises a number of quite general physics problems. In this lecture, I’ll describe the efforts that my colleagues and I have been making to give these physics problems a precise formulation, and to get some first hints at the solutions, which we hope may be more universal. This has involved an interplay of theory and experiment, physics and biology, and we have had an enormous amount of fun, which I also hope to convey.
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