An advantage of translesion DNA polymerases is they can replicate ( ), but a disadvantage is they ( ).

Question

An advantage of translesion DNA polymerases is they can replicate (           ), but a disadvantage is they (                                    ).

BlackTom AI · Accepted Answer

Translesion DNA polymerases can replicate across lesions in the template strand that would stall high-fidelity replicative polymerases. Relevant concepts: normal replicative polymerases (Pol δ and Pol ε in eukaryotes) have tight active sites and 3'→5' exonuclease proofreading, so they cannot accommodate distorted bases or bulky adducts and will stall at damaged DNA. Translesion synthesis (TLS) polymerases (e.g., Pol η, ι, κ, Rev1) have more open active sites that tolerate distorted templates and non‑Watson–Crick bases, allowing DNA synthesis "over damaged DNA." This is the advantage.

Step-by-step reasoning:
1. A DNA lesion (thymine dimer, abasic site, bulky adduct) blocks replicative polymerase progression.
2. The replication fork stalls; to avoid collapse, TLS polymerases are recruited and replace the replicative polymerase.
3. TLS polymerases insert nucleotides opposite the lesion and often extend a short distance past it, after which replicative polymerases resume synthesis.
4. Mechanistically, TLS polymerases lack or have reduced 3'→5' exonuclease proofreading and have looser active sites, so they make more mistakes when incorporating nucleotides—this yields low fidelity.

Why the correct answer is correct: the main functional benefit of TLS polymerases is their ability to synthesize DNA across damaged templates (over damaged DNA). Their structural and enzymatic properties that enable bypass also reduce accuracy, producing higher error rates (low fidelity), which is the principal disadvantage.

Why other choices are incorrect:
- "very quickly, have low fidelity": speed is not the defining advantage; TLS is often slower or similarly paced and focused on bypass, not speed.
- "over damaged DNA, are very slow": being very slow is not the characteristic disadvantage; the key drawback is error-proneness.
- "very accurately, are very slow": TLS polymerases are not very accurate; they are error-prone.

Conclusion: the correct choice is "over damaged DNA, have low fidelity," matching the provided answer.

An advantage of translesion DNA polymerases is they can replicate ( ), but a disadvantage is they ( ).Single choice

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