Discovering the lac operon, François Jacob
Interviewee: François Jacob. François Jacob talks about bacterial mutants that could not metabolize lactose. Using these mutants, Jacob and Monod figured out how protein production is controlled. (DNAi Location: Code > Controlling the code > Players > François Jacob and Jacques Monod > Making mutants)
Well, Monod started to make mutants, he made mutants which were unable to use lactose, that is to eat lactose and to metabolize lactose, and he showed that in these, some of these mutant there was no galactosidase made. So, that was a gene, which controlled the synthesis of galactosidase. Then they found also that there was another gene closely adjacent, which turned out to be adjacent to the first one, which had to do with the entry of lactose in the cell, and they called that permease. So, bacteria could become unable to utilize lactose, either because they were unable to make the enzyme, which cut the lactose, or because they became unable to concentrate lactose in the cell. In addition, in most wild type E. coli, that is the E. coli you find in nature or in the guts of all of us, the enzyme is inducible as we said, that is, it's made only in the presence of galactoside. But they also found, the Monod group found that there are mutants, which are able to make the enzyme without the galactoside. So the first one, which is the normal, we are call inducible, and the other one was called constitutive. And the question was, why is it constitutive?
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François Jacob explains why Jacques Monod chose to work with the lactose system.
François Jacob talks about the relationship between DNA, ribosomes, and protein production.
François Jacob talks about how enzyme production was viewed at the time they were beginning their experiments.
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 Genes control the structure of proteins
Jacques Monod and François Jacob work with how bacteria breaks large sugars into smaller pieces.
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 talks about how he and Jacques Monod named messenger RNA.
François Jacob, Sydney Brenner and Matt Meselson worked on the role of mRNA. An on/off switch involving mRNA seemed a logical control point for protein production.
François Jacob and Jacques Monod were the first to discover how genes were turned on and off.