Question:

The lac operon is an example of

Updated On: Aug 1, 2022
  • repressible operon
  • overlapping genes
  • arabinose operon
  • inducible operon.
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The Correct Option is D

Solution and Explanation

The two French scientists, Jacob and Monod proposed the lac operon of E. coli. The lac operon (an inducible operon) contains a promoter, an operator, a regulator gene and three structural genes z, y, and a, coding for the enzyme ??galactosidase,??galactoside permease, and ??galactoside transacetylase, respectively. P-galactoside permease 'pumps' lactose into the cell, where P-galactosidase cleaves it into glucose and galactose. The function of the transacetylase is still not clear. The lac regulator gene, designated the i gene, codes for a repressor. In the absence of the inducer (i.e., lactose, actually allolactose), the repressor binds to the lac operator sequence, preventing RNA polymerase from binding to the promoter and transcribing the structural genes. The inducer of the operon, allolactose, is derived from lactose in a reaction that is catalyzed by (?? galactosidase. Once formed, allolactose binds to the repressor, causing it to be released from the operator is doing so, it induces transcription of the z, y and a structural genes. CAP is activator called catabolic activator protein. It exerts a positive control in lac operon because in its absence RNA polymerase is unable to recognise promotor gene. CAP activates lac genes only when glucose is absent. Such enzymes whose synthesis can be induced by adding the substrate are known as inducible enzymes and the genetic systems responsile for the synthesis of such an enzyme are known as inducible operons.
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Concepts Used:

Regulation of Gene Expression

The process by which the instructions present in our DNA are converted into a functional product, such as a protein is called Gene Expression. It is a tightly coordinated process that allows a cell to respond to its changing environment.

In the meanwhile process, genetic codes from the DNA code are converted into a protein with the help of translation and transcription. The genetic expression shows the process of the genetic makeup of an organism as its physical traits. All over the process, the information flows from genes to proteins.

For a better understanding, let us take the example of the Keratin genes. Keratin is a protein that helps in the formation of our hairs, nails, and skin. Usually, these things grow at a continuous speed as our hairs, nails, and skin get worn down over a period of time. The production of excessive keratin could form many hairs on the skin, dry and hard skin, and thick and long nails. To avoid this, it is necessary to regulate the expression of the keratin gene.

Regulation of gene expression includes different mechanisms through which our cells manage the amount of produced protein by our genes.