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 double-strand break that occurs just after replication in an actively dividing cell

Accepted Answer

Hi, everyone. Let's move on to our next question. It says which of the following is a bypass mechanism that permits the DNA polymerase to duplicate beyond a damaged region in the DNA. Perhaps introducing mutations. Choice, a trans lesion synthesis T L S B nucleotide, excision repair, N er choice C base excision repair B er or choice D direct reversal D R. So we're thinking about a mechanism that allows DNA polymerase as it goes along to just keep going over a damaged region of DNA. I was kind of envision like a really rough patch of road or giant pothole and my truck rolling over it and we can be kind of guided by the names. Here we imagine something going over a lesion of DNA and keeping on going in the synthesis process. And the term we are looking for is choice a trans lesion synthesis. So imagine trans going past a lesion. So synthesis going over, going past a lesion. So that is this process that allows the DNA polymerase to keep going. It is error prone because there's no template that's being used. The enzymes just insert bases opposite the damaged ones. So these can end up being incorrect and mutations can be introduced. However, this is still an important method because without it, we're talking about areas of damage that are so drastic that DNA replication would just stop. That's obviously a really serious problem. And so we have this very error prone mechanism, it's not great, but it allows the cells to keep going and keep replicating. So that's why that mechanism is important. And again, that's a bypass mechanism to get past the damaged region in the DNA. Let's look at our other answer choices to understand why they're not correct. So, choice is B and C, we have two forms of excision repair, nucleotide, excision repair and base excision repair. Both of these as their names indicate um remove and replace damaged bases. The N er nucleotide excision repair repairs, bulky lesions in DNA. So you have areas where there's a damage that causes a distortion in our double helix. And the N er pathway then removes and replaces a patch of nucleotides to deal with that damage. In base excision repair, you have the removal. So it removes and replaces single damaged bases and these are not error prone processes because in both cases, you have a template to work from. So you're removing a base or a group of bases. But the correct base to replace the ones you're fixing can be determined by the fact that you still have a template strand there. So that's why choice B and C are not our correct answer. And then choice, the direct reversal. This is in sort of two specific kinds of damage where the damage is just directly repaired. So the damage is repaired, there's no need for a template. And the situations where this occurs are when you have pyrimidine diers that form as a result of exposure to U V radiation. So that causes these covalent bonds to form between neighboring Perine. This can cause a problem because it can cause mismatches if the dimer looks like a single base to the um DNA polymerase. So when these pyro diers form direct reversal can actually just break the covalent bonds. And it actually uses the system of repair, uses visible light to as energy in a process called photo reactivation. So that's one kind of damage that can just be directly reversed, break the erroneous covalent bonds. And then the other kind is when you have a male group added to a guanine base, this can cause a mismatch because it can cause it to bind to thymine or pair with thymine instead of cytosine. And you actually have an enzyme called methyl guanine methyl transferase. So M GMT enzyme just removes the metal group, thereby reversing the damage. So these processes directly reverse the damage to the DNA, allowing everything to go on properly. But again, it's a very different mechanism from this translation translation synthesis where you just have to, you know, bow your way past the damaged area. So that's why trace D isn't correct. So going back to our question, the bypass mechanism that permits the DNA polymerase to duplicate beyond damaged region. Perhaps introducing mutations, choice, a trans lesion synthesis T L S. See you in 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 double-strand break that occurs just after replication in an actively dividing cell

Key Concepts

Double-Strand Breaks (DSBs)

Homologous Recombination (HR)

Non-Homologous End Joining (NHEJ)

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 double-strand break that occurs just after replication in an actively dividing cell

Key Concepts

Double-Strand Breaks (DSBs)

Homologous Recombination (HR)

Non-Homologous End Joining (NHEJ)

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 double-strand break that occurs just after replication in an actively dividing cell