Interviewee: François Jacob. Designing bacteria.

The observation, was that if you look at bacteria growing on glucose, they don't make the enzyme galactosidase. The enzyme galactosidase, the galactose is made of two sugars, glucose and galactose, which are attached together. And the galactosidase cuts out and releases glucose and galactose. Now if you grow your cell on glucose as a carbon source, they don't produce the enzyme. If you grow them on galactose, or derivatives of galactose, they make the enzyme betagalactosidase. Now when you grow them on glucose and switch to lactose, there is a small delay before they produce the enzyme. And the problem of Monod was to understand what happens and when I arrived the theory was that the bacteria produce a molecule even without galactose, and when you add galactose the protein molds on galactose and that's why it becomes an enzyme.

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