The Operon Model

After Jacob and Monod ...

Prokaryotic cells must have the opportunity to control protein biosynthesis for an ecological use of energy. Otherwise, either too many or too few proteins would be formed.

Jacob (* 1920) and Monod (1910-1976) researched E. coli bacteria and found gene regulation through substrate induction and end-product repression.
Before going into detail, a few terms have to be clarified:

The operon is a DNA segment that RNA polymerase uses as a starting point in transcription. Promoter, operator and structural genes make up this sector:

 Promoter: serves as a starting point and starting point for RNA polymerase

 Operator: At this point, the repressor or activator docks

 Structural genes: contain the information about which proteins are to be synthesized

As long as there is no repressor on the operator, RNA polymerase, including the associated transcription, runs smoothly. The structural genes are read and new proteins are syntethisiert.

If a repressor binds to the operator, it alters its structure and prevents the RNA polymerase from draining off. Thus, the transcription is stopped -> The protein biosynthesis comes to a standstill.

This scheme also works the other way around, ie with activators that dock to the operator and thus enable the transcription by RNA polymerase.

Summary

The operon allows the transcription of genes to be turned on and off.

Depending on the operon, gene regulation may be through substrate induction as well as end product repression.