Using your knowledge of DNA repair pathways, choose the ...

Question

Using your knowledge of DNA repair pathways, choose the pathway that would be used to repair the following types of DNA damage. Explain your reasoning.

a thymine dimer induced as a result of UV exposure

Accepted Answer

Welcome back, everyone. Let's look at the next problem. It says which of the following pathways is responsible for repairing helix distorting DNA damage. Choice A mismatch repair. M M R. Choice B, nucleotide excision repair and er choice C base excision repair, B er or choice D direct reversal D R. Well, Helix's distorting DNA damage is going to be repaired by choice. B nucleotide excision repair, it can be rather tricky to keep straight N er nucleotide excision repair versus B er base excision repair. Even their names are so similar. But nucleotide excision repair replaces an entire patch of nucleotides. Well, base excision repair replaces a single base. So when we talk about helix distorting DNA, we can imagine this is a sort of larger uh error, a larger lesion because it's large enough to actually distort the shape of the double helix. So it often requires excising and replacing a larger region. So N er is used when you have helix distortion and that can occur with things like U V radiation damage. This can cause the formation of Perine diers, covalent bonds between neighboring bases that can distort your DNA helix. It also can be caused by the addition of large chemical groups. This can happen when you have exposure to a muto genetic chemical, for instance, and large chemical groups get stuck onto your bases big enough to actually distort that double helix. Whereas basic excision repair just replacing a single base occurs when you have a single damaged base or sometimes the addition of a small chemical group that shouldn't be there but not big enough to distort the helix itself. So B er for small issues, just cutting out and replacing one single base n er nuclear tied excision repair when you have something that's actually affected the structure of your double helix and need a larger excision and repair. So we can go ahead and eliminate after this discussion base excision repair. As we are looking at helix distorting DNA damage and then looking at our other answer choices, mismatch repair is when you just have a base mismatch kind of obviously. So you have a paired with G instead of T or something like that. And so there's a pathway to replace that, recognizing the template, the correct base by its methylation status and then excising and replacing the mismatched base in the new strand, which is not methylated yet. And that's how the system distinguishes those two. So chose not correct. And then finally, joys the direct reversal when you have an actual just correction of the error to the DNA. So this can happen when you have removal of covalent bonds. So it is a method of repair in terms of U V damage. So formation of say a thymine dimer, you might have direct repair of that rather than removing a whole patch of nucleotides, you could have just direct breakage of those Kent bonds. There's a repair mechanism called photo reactivation. When visible light is used to catalyze the breaking of those bonds. And another way form of direct reversal is when you have the removal of methyl groups from guanine, sometimes a methyl group gets put on a guanine which can cause a mismatch. It will bind to the wrong base or complement the wrong base. And there's an enzyme that actually can just pop that methyl group off directly repairing something that would lead to an error, but that's not what we're talking about here. Choice. Choice D is not our answer. So again, pathway responsible for repairing helix distorting DNA damage, choice B, nucleotide excision repair. See you on the next video.

Using your knowledge of DNA repair pathways, choose the pathway that would be used to repair the following types of DNA damage. Explain your reasoning.

a thymine dimer induced as a result of UV exposure

Key Concepts

Thymine Dimers

Nucleotide Excision Repair (NER)

DNA Repair Pathways

Watch next

Using your knowledge of DNA repair pathways, choose the pathway that would be used to repair the following types of DNA damage. Explain your reasoning.a thymine dimer induced as a result of UV exposure

Key Concepts

Thymine Dimers

Nucleotide Excision Repair (NER)

DNA Repair Pathways

Watch next

Using your knowledge of DNA repair pathways, choose the pathway that would be used to repair the following types of DNA damage. Explain your reasoning.

a thymine dimer induced as a result of UV exposure