DNA Structure and Replication · USMLE Step 1

If a toxin specifically inhibited DNA primase, which process would be directly impaired during DNA replication?

  1. Unwinding of the parental DNA double helix
  2. Removal of RNA primers from the new strands
  3. Synthesis of RNA primers to initiate DNA synthesis
  4. Ligation of adjacent Okazaki fragments together
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Correct answer: Synthesis of RNA primers to initiate DNA synthesis

Primase synthesizes the short RNA primers needed to provide a 3′-OH starting point for DNA polymerase; without primase, no DNA synthesis can begin on either strand.

Difficulty: Medium Question 19 of 20

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