Gene Regulation

Gene Regulation

The Operon

The Operon

 

Four regions of DNA control the production of a protein such as the enzyme Beta-galactosidease;

 

•        a structural gene that holds the codons for the amino acid sequence found in the enzyme.
•        an operator region right in front of the structural gene.
•        a promotor region where the RNA making enzyme will bind to the DNA.
•        a regulator gene which has a role in controling the transcription from the structural gene.

 

The combined region of the operator and structural gene is called an operon.

Summary :

Many genes are ....


... normally blocked by the action of a repressor protein. This prevents the RNA polymerase enzyme from binding to the gene and transcribing the structural gene. Such genes are induced by the arrival of an inducer molecule which binds to the repressor protein and rendering it inactive. This allows transcription from the structural gene and the production of a protein.

Other genes are normally active and able to be constantly transcribed, because the repressor protein is produced in an inactive form. On the arrival and binding of the corepressor molecule the complex can act as a functional repressor and block the structural gene by binding at the operator site.

These genes are therefore either inducible or repressible.