Trading bits in the readout from a genetic network

In genetic networks, information of relevance to the organism is represented by the concentrations of transcription factor molecules. In order to extract this information the cell must effectively “measure” these concentrations, but there are physical limits to the precision of these measurements. We explore this trading between bits of precision in measuring concentration and bits of relevant information that can be extracted, using the gap gene network in the early fruit fly embryo as an example. We argue that cells in the fly embryo can extract all the available information about their position if the concentration measurements approach the physical limits to information capacity, and that realistic molecular mechanisms can reach these abstract bounds if their parameters are selected appropriately.