The essence of molecular genetics lies in the discovery of a special class of highly polymeric molecules, the nucleid acids. These molecules function in the cell in very much the same manner in which the punched tapes of modern computers function. Four types of punch markings are employed, and information is stored in very long linear tapes, containing sequences of many thousands of punch marks. The manner in which this information is copied and the manner in which it is transcribed is discussed. The conceptual system discussed in this lecture occupies a central role in modern biology. It is a surprising fact that both the experimental findings and the conceptual developments originated - and still largely develo- outside the walls of academic biology, conceived as Zoology and Botany. The sociological reasons for this bizarre situation are discussed. Resume L'essentiel de la gen