Molecular biology, a widely used expression for a changeable meaning

The present article is the on-line equivalent of Preprint 310 of the Max-Planck-Institut für Wissenschaftsgeschichte (Berlin) and has been contributed as an oral communication in September 2005.On my side, I believe that I first encountered the expression “molecular biology” at the very beginning of my thesis work, in October 1964, when seeing an issue of the Journal of Molecular Biology, a journal then considered in the laboratory the smartest of the best journals in modern biology. However, even in Monod's and Jacob's laboratories, the words “molecular biology” were not in routine use among us, whereas bacterial genetics, gene expression, negative and positive regulation, models, biophysics, operon, replication and replicon, etc were much more frequently used to speak of what was going on. In my opinion, the stepwise generalization of the use of “molecular” and “molecular biology” reflects distinct periods of doing science through molecular approaches, but does not attribute a unified meaning to the expression “molecular biology”