The Operon Theory

All enzymes are made of protein, all proteins are made of amino acids, and all amino acids have a DNA codon. Basically, DNA controls RNA which controls the production of proteins.

In 1961, François Jacob and Jacques Monod proposed the Operon Theory to explain how cells control the production of enzymes.

The following is a list of the components of the operon.

• The regulatory gene codes for the repressor protein.
  
  
• The promoter site is the attachment site for RNA polymerates.
  
  
• The operator site is the attachment site for the repressor protein.
  
  
• The structural genes code for the proteins.
  
  
• The repressor protein is different for each operon and is custom fit to the regulatory metabolite. Whether or not the repressor protein can bind to the operator site is determined by the type of operon.
  
  
• The regulatory metabolite is either the product of the reaction or the reactant depending on the type of operon.
  
  
• The messenger RNA.
  
  
• The final enzyme.

There are two kinds of operons: repressible and inducible.

• In the repressible operon, the product is the regulatory metabolite. When the concentration of the product increases, the product binds to the repressor protein allowing the repressor protein to bind to the operator site -- shutting the operon down.
  
  
• In the inducible operon, the reactant is the regulatory metabolite. When the concentration of the reactant increases, the reactant binds to the repressor protein removing the repressor protein from the operator site -- turning the system on.