This review summarized the experiments on the regulation of the lacZ gene encoding beta galactosidase in E. coli and on phage lambda lysogeny. It formulated for the first time the hypothesis that genes are regulated at the transcriptional level by specific regulatory genes and that these regulators (proteins or RNA) respond to metabolic changes, environment etc. It emphasized the role of short-lived RNA identified by F.Gros et al. and S.Brenner et al. as an intermediate between genes and their protein products. The Operon paradigm can be considered as one of the major milestones in the emergence of Molecular Biology in the second half of the 20th century.

The 50th anniversary of this publication will be celebrated with a special symposium to be held at the Pasteur Institute in Paris between the 17th and the 20th of May 2011. We will attempt to trace the influence of this discovery on the way molecular biology has progressed in the last half century. A number of distinguished scientists will review our present knowledge on gene expression control, epigenetics, stem cells and development, cell growth and division and systems biology among others.

- Historical perspectives
- Mechanisms of transcription
- Epigenetics
- Stem cells and development
- Transcription and differentiation
- Cell growth and division
- Networks and systems biology