Genes control the structure of proteins, François Jacob
Interviewee: François Jacob. Genes control the structure of proteins. (DNAi Location: Code > Controlling the code > Putting it together > The lac operon)
So by comparing the system of the viruses, the lysogenic bacteria on the one hand and the induced synthesis of galactosidase, it was clear that it was two very similar system, and by comparing this system we came to a model which I am trying to describe now, the idea what you had a gene controlling the structure of proteins, which we called structural gene, and we can call that SG-1, SG-2, cloned to each other, for instance the Z gene of galactosidase and the Y gene permease. And somewhere else, which could be either far or close to the other, a regulatory gene, that is a gene, which control the expression of these two structural genes. So the idea were that from this you had a messenger, that the gene which is, it's DNA, a messenger which was RNA, and from this messenger proteins were done. So that goes like that. Now the regulation was by, what we call this negative system, that is a regulatory gene made a product, which at first we thought was RNA but finally was protein, so it made a protein which we called a repressor. And this repressor was acting on a small sequence of DNA adjacent to the structure, which we called the operator. So there was here, so the regulatory gene produced a repressor, a protein, which binds to a specific sequence, which is the operator, which control the initiation of messenger production. And the lactose that is the inducer, was supposed to interact with the repressor and prevent him from attaching to the operator. So the repressor was a double-sided structure, one which recognize the operator and the other which recognize the small molecule, the lactose. And this we call the negative system because it blocked, so that was the model, which we call operon, 'ron', with 'on'.
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Small image of François Jacob's lac operon drawing.
Jacques Monod and François Jacob work with how bacteria breaks large sugars into smaller pieces.
François Jacob talks about bacterial mutants that could not metabolize lactose. Using these mutants, Jacob and Monod figured out how protein production is controlled.
François Jacob talks about the relationship between DNA, ribosomes, and protein production.
Francois Jacob and Jaçques Monod figured out how bacteria controlled the production of an enzyme called beta-galactosidase. This system of feedback and negative regulation became the lac operon and was the first model for the control of protein productio
François Jacob talks about how enzyme production was viewed at the time they were beginning their experiments.
Walter Gilbert talks about identifying the lac operon repressor.
François Jacob explains why Jacques Monod chose to work with the lactose system.
The first model for the control of protein production was the lac operon. This system of feedback and negative regulation is used by bacteria, however, the general principles also apply to higher organisms. Another method of protein regulation involves
François Jacob and Jacques Monod were the first to discover how genes were turned on and off.