The lac operon consists of
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Lactose commonly known as milk sugar is a β-galactoside. E. coil uses lactose as an energy and a carbon source. Lactose is broken down into glucose and galactose. The products of lactose (lac) operon consisting of an operator, promoter, and three structural genes are metabolized.
- Four regulatory genes only
- Two regulatory genes and two structural genes
- Three regulatory genes and three structural genes
- One regulatory gene and three structural genes
The Correct Option is D
Solution and Explanation
The lac operon consists of one regulatory gene and three structural genes.
The lac operator is a short region of DNA that consists of a promoter, an operator, a regulator gene, and three structural genes z, y, and a. The lac operon interacts with a regulatory protein lac repressor that negatively controls the transcription of the operon. The three structural genes are:
- lac z- codes for the enzyme β-galactosidase. This cleaves the lactose molecule to give glucose and galactose. This enzyme is also responsible for converting lactose to allolactose.
- lac y- codes for the permease that transports lactose into the cell.
- lac a- codes for acetyltransferase (or β-galactoside transacetylase). This particular operon is controlled by both positive and negative regulation.
It was two French scientists, Jacob and Monod who proposed the lac operon of E. coli.
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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.
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