Name: Lac Operon
Uploaded: 2019-07-19
Duration: 9 min 11 s
Description: A lac operon is a group of genes with a single promoter The genes in the operon encode proteins that allow the bacteria to use lactose as an energy source. L...

Question

Explain the inducible system of an operon with a proper illustration.

Accepted Answer

An operon is a genetic unit comprising of a cluster of adjacent, co-ordinately controlled structural genes which produce a single polycistronic mRNA that codes for different enzymes required for a single metabolic pathway. Basically, there are two types of operon –Inducible and repressible, depending on the transcriptional state. In inducible operons, transcription is normally not taking place and certain substance (inducer) can induce transcription.

Following are the characteristics of an inducible system:

Normally the gene is found in the turned-off condition.

Expression of genes is turned on in response to a substance called inducer in the environment.

The ultimate product of the genes is known as inducible enzymes.

The synthesized enzymes are involved in the catabolic (degradative) pathway of biochemical reactions.

The effector substance is an inducer meant for induction by which the rate of enzyme synthesis is increased.

When there is no induction, the active free repressor binds to the operator and turns off transcription.

When the inducer is present it binds with the repressor and inactivates the repressor so that the inactivated repressor-inducer complex cannot bind with the operator gene.

On induction, the operator site remains open, and the RNA polymerase enzyme can move to the structural gene to carry out transcription.

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