What enzyme relieves supercoiling ahead of the replication fork?

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Multiple Choice

What enzyme relieves supercoiling ahead of the replication fork?

Explanation:
Relief of supercoiling ahead of the replication fork is handled by topoisomerases. As helicase unwinds the DNA, positive supercoils build up ahead of the fork, which would impede further unwinding. Topoisomerases transiently cut one or both DNA strands, allow the helix to swivel or strands to pass through, and then reseal the breaks, relaxing the torsional stress. In bacteria, this role is carried out by DNA gyrase, a type II topoisomerase that relieves the positive supercoils (and can introduce negative supercoils). This activity is distinct from what DNA polymerase does (synthesis), what helicase does (unwinding without relief of torsion), or what primase does (primer synthesis).

Relief of supercoiling ahead of the replication fork is handled by topoisomerases. As helicase unwinds the DNA, positive supercoils build up ahead of the fork, which would impede further unwinding. Topoisomerases transiently cut one or both DNA strands, allow the helix to swivel or strands to pass through, and then reseal the breaks, relaxing the torsional stress. In bacteria, this role is carried out by DNA gyrase, a type II topoisomerase that relieves the positive supercoils (and can introduce negative supercoils). This activity is distinct from what DNA polymerase does (synthesis), what helicase does (unwinding without relief of torsion), or what primase does (primer synthesis).

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