In an E. coli strain the i gene gets mutated and its product can not bind the inducer molecule. If the growth medium is provided with lactose, what will be the outcome?
- Only z gene will get transcribed
- z, y, a genes will be transcribed
- z, y, a genes will not be translated
- RNA polymerase will bind the promoter region
The Correct Option is C
Solution and Explanation
If the i gene is mutated in such a way that the repressor molecule is unable to bind with the inducer, the repressor which is now free from the inducer will now bind to the operator sequence. This will prevent the binding of RNA polymerase on the promoter sequence. Lactose in the medium cannot bind to the repressor as effectively as allolactose does. Therefore, lactose also cannot deactivate the repressor and prevent it from binding to the operator.
Thus if the operator is blocked by the repressor, there will be no transcription and the structural genes z, y and a will not get transcribed and translated.
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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.
