What is the likely effect of each of the following mutations o...

Question

What is the likely effect of each of the following mutations of the trpL region on attenuation control of trp operon gene transcription? Explain your reasoning.

Two nucleotides are inserted immediately following the polypeptide start codon.

Accepted Answer

Hi, everyone. Here's our next question. It says, what is the possible effect of a mutation causing the insertion of two nucleotides in the middle of the trip L region? Well, before the polypeptide stop codon, we have choice. A, the mutation could result in the production of a truncated trip L protein which could interfere with the regulation of the trip operon B. The mutation could cause a frame shift leading to the production of a completely different protein with a different function than the original trip L protein choice C. The mutation could cause premature termination of translation of the trip L gene leading to the production of a nonfunctional or partially functional trip L protein choice D all of the above or E none of the above. So let's think through the situation we're presented with. So as we know the gene for the leader peptide, which would be, this trip is an essential part of the attenuation process of the trip operon. So when the leader peptide is completely synthesized, which happens when there is high levels of crypto, the li peptide has two trippin residues in it. So if tripp toan levels are low, the ribosome will pause for a while before it's able to continue. If crypto fan levels are high, that li peptide can be completely synthesized. There's plenty of trip to fan around and that leads to the attenuation of transcription of the trip upper on jeans if the leader peptide is not completely synthesized. So if that ribosome has to pause, so in conditions of low trapan, then that allows transcription to continue at the trip dreams. So transcription continues. So we're going to think about a scenario in which we've inserted two nucleotides in the middle of the gene for that li peptide. So we have a two nucleotide insertion in the middle, the middle of the gene. Well, what do we know can happen when we insert two nucleotides, we can cause a frameshift mutation. We've thrown off the reading frame going forward after that mutation. So with that in mind, let's walk through our answer choices. Remembering that we do have the possibility that all or none of them are correct. So choice A says the mutation could result in the production of a truncated trip L protein which could interfere with the regulation of the trip operon. Well, this is correct. Perhaps the insertion of those nucleotides will lead to a nonsense mutation in which we get a stop code on where there wasn't one before that could cause the production of a truncated protein. And since that peptide is a necessary part of the attenuation process that will interfere with the regulation. So we already have one correct answer. So we can eliminate choice E all of the above or none of the above. Excuse me. But let's keep going and look at choice B. Choice B says the mutation could cause a frame shift leading to the production of a completely different protein with a different function. Well, this is correct as we discussed, insertion of two nucleotides definitely can cause a frame shift which can then change all the amino acids downstream. So choice B is correct. Well, if I'm in a hurry, that's gonna lead me to choice D. All of the above, I already have more than one correct answer. So on a test, I just pick Choice B and move on. But in the interest of being thoroughly explaining everything, we will look at choice C, the mutation could cause premature termination of the translation of the trip L gene leading to the production of a nonfunctional or partially functional trip L protein. And that is true. Again, we're going to disrupt the translation of that gene due to this insertion in the middle of the gene. So all of these are true and therefore our answer here is choice D all of the above. See you in the next video.

What is the likely effect of each of the following mutations of the trpL region on attenuation control of trp operon gene transcription? Explain your reasoning.
Two nucleotides are inserted immediately following the polypeptide start codon.

Key Concepts

Attenuation Control

Mutations and Their Effects

RNA Secondary Structures

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