DNA replication enzymes — Which enzyme adds complementary bases to the growing DNA strand during replication?

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Solve this multiple-choice question and choose the correct option.

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Introduction:Replication requires a template, primers, and enzymes that catalyze phosphodiester bond formation. This question focuses on the enzyme that actually polymerizes deoxyribonucleotides into DNA by base pairing with the template strand. Given Data / Assumptions: Complementary base pairing guides nucleotide selection. DNA polymerases require a primer with a free 3′-OH. Synthesis proceeds in the 5′→3′ direction only. Concept / Approach:Identify the role of each enzyme: helicase unwinds, primase lays RNA primers, DNA polymerase extends DNA, ligase seals nicks, and RNA polymerase transcribes RNA, not DNA. Therefore, DNA polymerase is responsible for adding complementary bases to DNA during replication. Step-by-Step Solution: 1) Generate primers (by primase) to provide a 3′-OH.2) DNA polymerase catalyzes addition of dNTPs to the 3′ end, matching A with T and G with C.3) Proofreading by many polymerases enhances fidelity. Verification / Alternative check:Biochemical assays show polymerase activity as template- and primer-dependent incorporation of labeled nucleotides into acid-insoluble DNA. Why Other Options Are Wrong: a) Helicase unwinds DNA; it does not polymerize nucleotides.b,c) Terms are nonspecific and not standard for the polymerizing enzyme.e) RNA polymerase synthesizes RNA, not DNA. Common Pitfalls:Using “replicase” generically; in eukaryotes, multiple DNA polymerases (e.g., δ, ε) share roles. Final Answer:DNA polymerase.

DNA replication enzymes — Which enzyme adds complementary bases to the growing DNA strand during replication?

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