Discovery
The operon model (Lac operon) of the regulation of gene expression in bacteria was proposed by Jacob and Monod and hey got noble prize in 1965 in Physiology and Medicine for this discovery.
Definition
“Operons are cluster of coregulated bacterial genes which regulate other genes responsible for protein synthesis”
Explanation
Operons were first studied in the bacterium E.coli, and they involve the enzyme of lactose metabolism and tryptophan biosynthesis.
Structure of Operon
Operon is generally composed of three basic DNA components:
1. Promotor:
It is a nucleotide sequence which is recognized by RNA polymerase and initiate transcription.
2. Operator:
It is a segment of DNA that is present between the promotor and other genes to be transcribed. In presence of repressor, RNA polymerase is physically obstructed and cannot transcribe the genes. In the absence of repressor, operator is active and start transcription of other proteins.
3. Structural genes:
These genes are responsible for synthesis of targeted proteins under the influence of operator.
Example of operon model:
In bacteria two operon model have been extensively studied, these are:
a. Lac Operon, and
b. Tryptophan operon
