He was educated at L'Ecole Alsacienne in Paris then studied medicine at the Université Libre de Bruxelles graduating in 1934. He then worked at the University of Cambridge and at Princeton University and at several institutes of marine biological research. Brachet was appointed Professor of Animal Morphology and General Biology at the Université Libre de Bruxelles and Research Director of the International Laboratory for Genetics and Biophysics in Naples.
In 1933 Brachet was able to show that DNA was found in chromosomes and that RNA was present in the cytoplasm of all cells. His work with Torbjörn Caspersson showed that RNA plays an active role in protein synthesis. Brachet also carried out pioneering work in the field of cell differentiation. Brachet demonstrated that differentiation is preceded by the formation of new ribosomes and accompanied by the release from the nucleus of a wave of new messenger RNA.
In 1934 he married Francoise de Baray.
In 1948 Jean Brachet was awarded the Francqui Prize for Biological and Medical Sciences.
- Embryologie Chimique (1944)
- Biological Cytology (1957)
- Introduction to Molecular Embryology (1957)
- Molecular Cytology (2 vols.) (1985)
- Sapp J., Jean Brachet, L'Hérédité Générale and the Origins of Molecular Embryology, History and philosophy of the life sciences (Hist. philos. life sci.), 1997, vol. 19, no 1 (dissem.), pp. 69-87, ISSN 0391-9714