Introduction

The bacterial genome has two different types of gene clusters: operons and regulons. A common regulatory system is accountable for the regulation of each gene cluster.

The contiguous or non-contiguous pattern of genes is the primary contrast between the operon and the regulon. In prokaryotes, the operon is a functional DNA unit of multiple genes controlled by a single promoter and an operator. A regulon is a functional genomic unit composed of a discontinuous set of genes regulated by a single regulatory protein. While the genes of a regulon can be distributed non-contiguously, the gene clusters of an operon are contiguously placed.

Different mechanisms are used in prokaryotes and eukaryotes to regulate gene expression. While eukaryotes utilise the notion of a regulon for their gene regulation, prokaryotes follow the concept of an operon to control the regulation of their genes.

What is Operon?
What is Regulon?
Difference between Operon and Regulon
Frequently Asked Questions (FAQs)

What is Operon?

An operon is a collection of genes whose expression is controlled in a coordinated method. The genes in the operon are contiguous. Thus, transcription of an operon produces a single polycistronic mRNA molecule. As a result, a single mRNA molecule is produced from the transcription of each gene within an operon. Thus, this polycistronic mRNA is translated to yield several functionally related proteins.

Many operons in the bacterial genome have been extensively studied, including the inducible Lac operon and the repressible Trp operon. The ability to collectively regulate this gene group under a single promoter is the primary significance of clustering the functionally related genes into operons. Because of this, they are transcribed together. Additionally, each operon only has one enhancer or repressor. A certain operon can therefore be either inducible or repressible.

Therefore, both the Lac operon and the Trp operon play a significant role in gene regulation and help cells conserve energy and maintain the accuracy of their molecular activities.

Also, read:Lac Operon – Regulation of Gene Expression

What is Regulon?

Regulons are collections of genes or operons controlled by a single regulatory process. A transcription factor, a type of regulatory protein, is what regulates this mechanism. These operons or genes can be found across the genome at various locations. However, each of them has a similar binding domain for a regulatory element or promoter that facilitates simultaneously regulating gene expression. The gene products of each of these operons are all functionally connected.

A group of regulons that can change in stress response is called a modulon. On the other hand, a stimulon is a group of genes expressed in response to a particular environmental stimulus. Because numerous regulons are involved, several regulatory mechanisms control the response.

In prokaryotes, a regulon comprises the genes required for arginine production. It has three single genes and two operons, totalling nine genes. Individual promoters are present in each of the five transcription units. However, they all use a repressor as a common operator. Another prokaryotic regulon accountable for the SOS response is exhibited in the presence of DNA damage.

Also, read:Gene Regulation

Difference between Operon and Regulon

Operon	Regulon
An operon is a group of related genes that have a single promoter	A regulon is a collection of genes or operons that respond to a specific signal by a single regulatory protein by turning on or off.
They are primarily found in prokaryotes.	They are found in both prokaryotes and eukaryotes
An operon is a group of contiguous genes found in a specific genome region.	The genes of a regulon are found in various regions within the genome.
Operons are of two types: repressible or inducible.	Regulons are also of two types: stimulon or modulon.
A single promoter regulates an operon.	An individual promoter is found in each transcription unit of a regulon.
They are also found in viruses like bacteriophages.	They are not found in viruses.
An operon transcribes a single polycistronic mRNA.	Each transcription unit of a regulon produces an individual, polycistronic or monocistronic mRNA.
Lac – operon, Trp – operon, His – operon, Ara – operon and Vol – operon	Ada regulon, FNR regulon and CRP regulon

All operon or regulon gene products are somehow functionally connected. Simply put, the genome position and the transcription unit type are the fundamental differences between operons and regulons.

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Frequently Asked Questions – FAQs

Give an example of a regulon in bacteria.

The operon-based genes for utilising maltose and the genes responsible for arginine production are two examples of regulons in E. coli. Twelve transport and biosynthesis genes make up the arginine regulon, dispersed over nine chromosomal regions.

What is the difference between operator and operon?

Three fundamental DNA components constitute an operon. A repressor’s binding site on DNA is called an operator. It is typically described in the lac operon as a section between the promoter and the operon’s genes.

What is the Lac operon model?

The Lac operon is a single-promoter operon or cluster of genes transcribed as a single mRNA. The operon genes produce proteins that enable lactose utilisation by the bacteria.