The segment of the bacterial TrpA gene involved in intrinsic t...

Question

The segment of the bacterial TrpA gene involved in intrinsic termination of transcription is the following; 3'-TGGGTCGGGGCGGATTACTGCCCCGAAAAAAAACTTG-5' 5'-ACCCAGCCCCGCCTAATGACGGGGCTTTTTTTTGAAC-3' Explain how a sequence of this typse leads to intrinsic termination of transcription.

Accepted Answer

Hi, everybody. Let's look at our next problem. It says the presence of A G C rich sequence followed by a series of a residues in the DNA template strand results in a termination of transcription. Because choice A G C rich sequence in the R N A transcript forms a stem loop structure which destabilizes the R N A DNA hybrid and causes the R N A polymerase to pause choice B the series of U residues in the R N A transcript is weakly paired with the A residues in the DNA template strand. Choice C the weak interactions between the U residues in the R N A transcript and a residues in the DNA template strand is unable to hold the R N A DNA hybrid together leading to transcription termination or choice D all of the above. Well, we're looking at the termination of transcription that's a result of our DNA template having a G C rich sequence followed by a series of a residues. One little note here is that this describes a factor, independent transcription termination because all you need is this particular uh element in the DNA template template to end transcription. Nothing else there's also factor dependent transcription termination that requires a protein called the row factor. But here we're talking about the factor independent version. So we recall that we do have that choice all of the above. So let's look a little more closely at these answer choices. In choice. A, it says that a stem loop structure is formed with that G C rich sequence in the R N A transcript. Well, this does happen with that G C rich sequence. It can bind to itself to form that stem loop structure. And this does indeed destabilize the R N A DNA hybrid which pauses the R N A polymerase. So choice A is correct. But since we have all of the above choice, I'm not going to pick it as my answer, I'll just mark it with a dot To show that it is a correct statement, then I get to choice B and it says the series of U residues in the R N A transcript is weekly paired with the A residues in the DNA template strand. And that's connected to choice C which says that this series of U residues paired with the DNA A residues, which is weakly paired that because of that weak, those weak interactions, that R N A DNA hybrid isn't held together very well. It pulls apart and transcription terminates. And these two statements are both correct. That is the result of those series of a residues in the DNA template strand, so since all of our answer choices are correct, our actual answer is choice d all of the above for the reasons that when you have a G C rich sequence followed by a series of a residues in your DNA template, this will result in the termination of transcription. See you in the next video.

The segment of the bacterial TrpA gene involved in intrinsic termination of transcription is the following; 3'-TGGGTCGGGGCGGATTACTGCCCCGAAAAAAAACTTG-5' 5'-ACCCAGCCCCGCCTAATGACGGGGCTTTTTTTTGAAC-3' Explain how a sequence of this typse leads to intrinsic termination of transcription.

Key Concepts

Intrinsic Termination of Transcription

Hairpin Structure Formation

Role of Poly-U Sequence

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