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The PA JA MO-PA JA MA experiment

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The Operon model
François Jacob Scientist
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Oui alors ça c'était la grande plaisanterie d'utiliser le même mot pour désigner des choses dont on estimait qu'elles étaient complètement différentes. Et puis c'est seulement peu à peu, que- En analysant chacun des systèmes, on s'est aperçu qu'il y avait d'étranges ressemblances entre les deux systèmes, et que finalement, ça menait à un modèle expérimental commun. Et ce modèle, c'était le modèle dit de l'Operon, à savoir que- Il y avait des gènes de structure qui gouvernaient la synthèse d'une ou plusieurs protéines, et qu'il y avait des gènes régulateurs qui fabriquaient- Ça on l'a pas décrit encore- qui fabriquait un produit. Alors on a mis beaucoup de temps à comprendre ce qu'il faisait. Qui faisait un produit cytoplasmique qui agissait pour moduler l'activité de l'autre. Et on a hésité, on a d'abord pensé que c'était un acide nucléique, parce qu'à cette époque-là, personne n'avait encore parlé de l'affinité des protéines, qu'il y avait des protéines qui avaient des affinités pour les acides nucléiques. Puis très vite, on a été conduit à penser que c'était une protéine parce qu'il y avait les mutants de régulation, donc du système de régulation, qui étaient sensibles à des- comment ça s'appelle déjà ? Qui remplace un- Ça alors c'est le bouquet- Non, non. Suppresseurs, non ? Suppresseurs, exactement. Des gènes suppresseurs, dont on savait qu'il remplaçaient un acide aminé par un autre, ou qu'ils mettaient un acide aminé là où il y avait un trou.
Yes, the biggest joke was to use the same word to qualify things that we considered to be completely different. And it was only little by little that- by analysing each of the systems, we noticed that there were strange similarities between the two systems, and that eventually, it lead to a shared experimental model. And that model, was the so-called Operon model, namely that- there were structural genes that ruled the synthesis of one or several proteins, and that there were regulator genes that made- We haven't described that yet- which made a product. It took us a long time to understand what it did. That it made a cytoplasmic product that acted to regulate the other's activity. And we hesitated, at first we thought that it was a nucleic acid because at the time, no one had talked about the protein affinity yet, that there were proteins that had affinities with nucleic acids. Then very quickly, we were lead to believe that it was a protein because there were regulator mutants, thus of the regulatory system, which were sensitive to- what are they called again? That replace the- that's incredible- No, No- Suppressor, isn't it? Suppressor, exactly. Suppressor genes, which we knew were replacing an amino acid by another, or which placed an amino acid where there was a hole.

François Jacob (1920-2013) was a French biochemist whose work has led to advances in the understanding of the ways in which genes are controlled. In 1965 he was awarded the Nobel Prize in Physiology or Medicine, together with Jacque Monod and André Lwoff, for his contribution to the field of biochemistry. His later work included studies on gene control and on embryogenesis. Besides the Nobel Prize, he also received the Lewis Thomas Prize for Writing about Science for 1996 and was elected a member of the French Academy in 1996.

Listeners: Michel Morange

Michel Morange est généticien et professeur à L'Université Paris VI ainsi qu'à l'Ecole Normale Supérieure où il dirige le Centre Cavaillès d'Histoire et de Philosophie des Sciences. Après l'obtention d'une license en Biochimie ainsi que de deux Doctorats, l'un en Biochimie, l'autre en Histoire et Philosophie des Sciences, il rejoint le laboratoire de Génétique Moléculaire dirigé par le Professeur François Jacob à l'Institut Pasteur. Ses principaux travaux de recherche se sont portés sur l'Histoire de la Biologie au XXème siècle, la naissance et le développement de la Biologie Moléculaire, ses transformations récentes et ses interactions avec les autres disciplines biologiques. Auteur de "La Part des Gènes" ainsi que de "Histoire de la Biologie Moléculaire", il est spécialiste de la structure, de la fonction et de l'ingénerie des protéines.

Michel Morange is a professor of Biology and Director of the Centre Cavaillès of History and Philosophy of Science at the Ecole Normale Supérieure. After having obtained a Bachelor in biochemistry and two Ph.Ds, one in Biochemistry, the other in History and Philosophy of Science, he went on to join the research unit of Molecular Genetics headed by François Jacob, in the department of Molecular Biology of the Pasteur Institute, Paris. Together with Olivier Bensaude, he discovered that Heat Shock Proteins are specifically expressed on the onset of the mouse zygotic genome activation. Since then he has been working on the properties of Heat Shock Proteins, their role in aggregation and on the regulation of expression of these proteins during mouse embryogenesis. He is the author of "A History of Molecular Biology" and "The Misunderstood Gene".

Duration: 1 minute, 43 seconds

Date story recorded: October 2004

Date story went live: 24 January 2008