Transcriptional regulation of operon gene expression involves the...

Question

Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following:

inducer

Accepted Answer

Hi, everybody. Here's our next question. Which of the following statements best describes the role of lactose in the context of lac operon regulation. Choice. A lactose binds to the regulatory molecules and inhibits transcription. B lactose binds to the repressor molecule, thereby preventing it from binding to the promoter region. Choice C lactose is produced by anaerobic respiration in the bacteria and helps activate the operon and choice D lactose that is present in the environment binds to a regulatory protein thereby inducing the expression of operon. So, first of all, we've got an easy one to eliminate right away. Choice. C says lactose is produced by anaerobic respiration, but it's lactic acid or lactate that's produced by anaerobic respiration, not lactose, they sound very similar but they're not the same molecule. So we can rule out choice C right away. As we recall, our lack operon is controlling the expression of genes that produce the proteins necessary to metabolize lactose and therefore the presence of lactose induces transcription, transcription is repressed when there's no lactose present. Since then those genes are not needed. So, keeping that in mind, let's look at our other answer. Choices. Choice A says lactose binds the regulatory molecules and inhibits transcription. While that would be incorrect, you don't want lactose inhibiting transcription. You want it to stimulate transcription. So choice A is not correct. Then choice B says lactose binds to the repressor molecule, thereby preventing it from binding to the promoter region. Well, this one is correct. The lac gene operon genes are usually repressed when they're not needed. So, a repressor molecule is bound to what's called the operator. The operator prevents, excuse me, the repressor protein prevents transcription because the operator is overlapping the promoter. So it's part of this promoter region. And when the repressor molecules present there, R N A polymerase is prevented from binding to the promoter and transcription is prevented. So this is a correct description of the role of lactose. When lactose binds to that repressor molecule, the repressor is released from its binding site and transcription can take place. Finally, to be thorough. Let's look at choice of D says lactose that is present in the environment binds to a regulatory protein, thereby inducing the expression of operon. Well, not quite correct. It binds to the lac repressor protein which releases it from the operator. So again, we were looking for the best description of the role of lactose when talking about the la operon. And the answer is choice B lactose binds to the repressor molecule thereby preventing it from binding to the promoter region. See you in the next video

Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following: inducer

Key Concepts

Inducer

Operon

Transcriptional Regulation

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