In the medium where E.coli was growing lactose was added which induce the lac operon. Then why does lac operon shut down some time after addition of lactose in the medium?
Solution and Explanation
Lac operon is a segment of DNA that is made up of three adjacent structural genes namely an operator gene a promoter gene and a regulator gene. It works in a coordinate manner to metaboilize lactose into glucose and galactose.
In lac operon lactose acts as an inducer. It binds to the repressor and inactivates it. Once the lactose binds to the repressor RNA polymerase binds to the promoter region. Hence three structural genes express their product and respective enzymes are produced. These enzymes act on lactose so that lactose is metabolized into glucose and galactose.
After sometime when the level of inducer decreases as it is completely metabolized by enzymes it causes synthesis of the repressor from regulator gene. The repressor blinds to the operator gene and prevents RNA polymerase from transcribing the operon. Hence transcription is stopped. This type of regulation is known as negative regulation.
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Construct and label a transcription unit from which the RNA segment given below has been transcribed. Write the complete name of the enzyme that transcribed this RNA.
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DNA strand:
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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.
