Quelques aspects moléculaires de la cytologie et de l'embryologie.

Our present knowledge of the cell structure, which is largely based on electron microscopy, is compared with what was known a few decades ago, when only light microscopy was available to the cytologist. The importance of cytochemical methods for the detection and localization of macromolecules (nucleic acids, proteins) is stressed. But it is pointed out that further analysis, with biochemical techniques, was required in order to understand the actual mechanisms of macromolecule synthesis in the cell (in particular, the relationships existing between nucleic acids and protein synthesis). The importance of genetical analysis in simple systems such as viruses and bacteria for the development of ‘molecular’ biology is then emphasized: in particular, the work of Avery identifying the ‘transforming principle’ with DNA, of Beadle leading to the ‘one gene, one enzyme’ theory, of the virologists who demonstrated that it is the nucleic acid component of viruses which carries the genetical information, have been of fundamental importance for the development of modern biology. No less important has been the work of the X‐ray crystallographers (Crick and Watson, Perutz, Kendrew, etc.) who established the fine structure of nucleic acids and of proteins. A brief review and a schematic representation of present ideas regarding the control exerted by DNA on the synthesis of specific proteins are then given: the main characteristics of the different kinds of RNA's, their interactions for the formation of polysomes, the role of the latter in protein synthesis, the main principles of the genetic codes, are briefly summarized. But cells are, in many respects, more complicated than bacteria. The concepts of molecular biology cannot be applied to cell differentiation without a recognition of the greater complexity of animal and plant cells. They represent, however, a most useful and powerful guide for research in that area: for instance, many aspects of morphogenesis in the unicellular al
Journal Article
Review
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