Information theory and the genetic code.

The genetic code, which directs the protein biosynthesis, is an information system. Although all its details are not known at present, its essential characteristics are elucidated, as well for the replication or transcription as for the translation of the genetic message. A coherent picture now appears, which reveals the existence of an universal structure, the most fundamental features of which seem to obey some logic. A systematic approach has been devised, which aims to their integration in a theorectical scheme: many features of the code table can thus be interpreted as resulting from a unique principle of best resistance against the effects of mutations. Any group of triplets or amino-acids can be considered along this line. It is more difficult however, to analyse the coexistence of two (or more) different groups. In this work, we propose to extend our optimization principle into a more general one, which includes the notion of information as defined by Shannon. We explore some consequences of this new principle in the most simple models that one can build for the origin and evolution of the genetic code.