DNA Structure and Replication · USMLE Step 1

Which feature of DNA’s structure provides the chemical basis for the semiconservative replication mechanism?

  1. Presence of short RNA primers on each strand
  2. Right-handed coiling of the double helix
  3. Antiparallel strands with complementary base-pairing
  4. Tight packaging of DNA around histone proteins
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Correct answer: Antiparallel strands with complementary base-pairing

DNA’s antiparallel strands and complementary A–T and G–C base-pairing allow each parental strand to serve as a template — enabling semiconservative replication.

Difficulty: Medium Question 18 of 20

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