Which enzyme relieves torsional stress ahead of the replication fork?

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Study for the DNA Replication and DNA Storage Test. Use flashcards and multiple choice questions, each with hints and explanations. Prepare for your exam with confidence!

Multiple Choice

Which enzyme relieves torsional stress ahead of the replication fork?

Explanation:
As the DNA double helix is opened by the helicase, the region ahead of the fork becomes overwound, creating positive supercoils that would slow or stop replication. Topoisomerase relieves this torsional stress by making transient breaks in the DNA backbone and allowing the strands to pass or rotate to unwind the excess twist, then resealing the breaks. This action smooths the progression of the fork. Primase lays down RNA primers, helicase unwinds, and ligase seals nicks after synthesis, but the enzyme specifically responsible for removing the torsional strain ahead of the fork is topoisomerase.

As the DNA double helix is opened by the helicase, the region ahead of the fork becomes overwound, creating positive supercoils that would slow or stop replication. Topoisomerase relieves this torsional stress by making transient breaks in the DNA backbone and allowing the strands to pass or rotate to unwind the excess twist, then resealing the breaks. This action smooths the progression of the fork. Primase lays down RNA primers, helicase unwinds, and ligase seals nicks after synthesis, but the enzyme specifically responsible for removing the torsional strain ahead of the fork is topoisomerase.

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