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
The question involves understanding the regulation of the lac operon in E. coli. The lac operon consists of three structural genes: z, y, and a, which are responsible for the metabolism of lactose. Regulation of this operon is mediated by the i gene, which codes for a repressor protein. This repressor binds to the operator region to prevent transcription of the operon unless an inducer, such as lactose, is present.
In the scenario described, the i gene is mutated, producing a repressor that cannot bind the inducer. As a result, the following occurs:
- Without a functional repressor binding to lactose, the repressor will continue to bind the operator region even in the presence of lactose.
- This continuous binding prevents RNA polymerase from transcribing the z, y, and a genes.
- The lack of transcription means that there will be no mRNA produced for these genes, hence they will not be translated into their respective proteins.
Therefore, despite the presence of lactose in the growth medium, the z, y, and a structural genes are not transcribed into mRNA and thus not translated into proteins.
The correct answer is: z, y, a genes will not be 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.
