The Physical Language of Molecules
Department of Physics, Weizmann Institute
In the living cell, information is carried by molecules. The outside environment and the biochemical circuitry of the cell churn out fluxes of molecular information that are read, processed and then stored in memory by other molecules. The cell's information-processing networks often need to translate a symbol written in one species of molecules into another symbol written in a different molecular language. This requires a code-table that translates between the two molecular languages. Perhaps the best-known example is the genetic code-table that translates sixty-four DNA base-triplets into twenty amino-acids. We discuss, in terms of information theory and statistical mechanics, the fitness of molecular codes as the problem of designing an optimal information channel. By incorporating this code fitness into population dynamics models, we suggest that the emergence and evolution of molecular codes may be explained by simple channel design considerations.