Difference between Regulator, Operator, Promoter and Structural Genes || The Operon System

 Operon is a part of genetic material which acts as a single regulated unit having one or more structural genes, an operator gene, a promoter gene, a regulator gene, a repressor and an inducer. Operator, promoter, and regulator genes constitute the regulatory region. Operon systems are common in prokaryotes. 

Regulator Gene:

1. It controls the functioning of operator gene

2. This produces a repressor or aporepressor for blocking operator gene.

3.It is commonly a large gene.

4. It functions through the formation of an mRNA of repressor.

Operator Gene:

1. It determines the functioning of structural genes.

2. This gene functions only when it is not blocked by a repressor.

3. The gene is small.

4. It functions through the presence or absence of repressor. 

Promoter Gene:

1. It is site for binding of RNA polymerase.

2. It is functional only when operator gene allows passage of RNA polymerase to structural genes

3.The gene is small.

4.It functions by providing recognition and binding sites for RNA polymerase.

Structural Gene:

1. The gene is connected with transcription of the formation of mRNA for synthesis of a particular polypeptide.

2.It functions only when it receives complementary nucleotides and RNA polymerase.

3. The gene is moderately long to large depending upon the polypeptide to be synthesized.

4.It functions through the formation of mRNA for structural or enzymatic polypeptide.