Localizing tymonucleic acid and zymonucleic acid within the cell: Jean Brachet’s research on the chemistry of cell differentiation

  • Alessandra Passariello «Sapienza», University of Rome
Keywords: Jean Branchet, Chemical embryology, nucleic acids, cell differentiation


The article reconstructs Jean Brachet’s research (1930-1950) on the role of nucleic acid metabolism in cell differentiation. In the late 1920s – early 1930s, when Brachet started his enquiry on the chemistry of cell differentiation, nucleic acids were distinguished into tymonucleic and zymonucleic acids, according to their respective localization in animal or yeast and plant cells. Brachet was the first to point to the coexistence of these two different macromolecules within the same cell type and suggest that variations in the production of tymonucleic and zymonucleic acid along the cell cycle are strongly correlated. The discovery fueled a rapid conceptual and terminological evolution in Brachet’s researches on the chemistry of cell differentiation. The prefixes tymo and zymo were dropped in favor of deoxyribo and ribo nucleic acids and protein synthesis was then conceived as the relationship between the two macromolecules.