Which enzyme synthesizes RNA primers during DNA replication?

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Multiple Choice

Which enzyme synthesizes RNA primers during DNA replication?

Explanation:
DNA replication relies on RNA primers to start synthesis because DNA polymerases cannot initiate strands from scratch; they can only extend from a pre-existing 3' end. The enzyme that provides this starting point is primase, a specialized RNA polymerase that makes a short RNA primer complementary to the DNA template. This primer gives DNA polymerase something to extend, allowing continuous synthesis on the leading strand and short fragments on the lagging strand that are later joined. After synthesis, the RNA primer is removed and replaced with DNA, and the gaps are sealed by ligase. Other enzymes have different roles: DNA polymerase builds DNA, not primers; topoisomerase relieves supercoiling; ligase seals nicks in the sugar-phosphate backbone.

DNA replication relies on RNA primers to start synthesis because DNA polymerases cannot initiate strands from scratch; they can only extend from a pre-existing 3' end. The enzyme that provides this starting point is primase, a specialized RNA polymerase that makes a short RNA primer complementary to the DNA template. This primer gives DNA polymerase something to extend, allowing continuous synthesis on the leading strand and short fragments on the lagging strand that are later joined. After synthesis, the RNA primer is removed and replaced with DNA, and the gaps are sealed by ligase. Other enzymes have different roles: DNA polymerase builds DNA, not primers; topoisomerase relieves supercoiling; ligase seals nicks in the sugar-phosphate backbone.

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