DNA Structure and Replication · USMLE Step 1

Which enzyme is responsible for unwinding the DNA double helix at the replication fork by breaking hydrogen bonds between base pairs?

  1. DNA polymerase
  2. RNA primase
  3. DNA helicase
  4. DNA ligase
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Correct answer: DNA helicase

DNA helicase unwinds the double helix by breaking hydrogen bonds between complementary base-pairs, creating single-stranded template DNA for replication to proceed.

Difficulty: Medium Question 2 of 20

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