Multiple Choice
During DNA replication, what stabilizes the unwound single-stranded DNA to prevent it from reannealing or forming secondary structures?
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8. DNA Replication
Overview of DNA Replication
Multiple Choice
In the overview of DNA replication, what is the primary role of topoisomerase at the replication fork?
A
It unwinds the DNA double helix by breaking hydrogen bonds between complementary bases.
B
It synthesizes short RNA primers needed to initiate DNA synthesis on the leading and lagging strands.
C
It relieves torsional strain (supercoiling) ahead of the replication fork by transiently cutting and rejoining DNA strands.
D
It joins Okazaki fragments together by sealing nicks in the sugar-phosphate backbone.
Verified step by step guidance1
Understand the context of DNA replication, where the double helix must be unwound to allow the replication machinery to copy each strand.
Recall that unwinding the DNA helix creates torsional strain (supercoiling) ahead of the replication fork, which can hinder the progress of replication.
Identify the enzyme responsible for relieving this torsional strain: topoisomerase. It does this by transiently cutting one or both strands of the DNA, allowing it to unwind and then rejoining the strands.
Differentiate the roles of other enzymes mentioned: helicase unwinds the helix by breaking hydrogen bonds, primase synthesizes RNA primers, and DNA ligase joins Okazaki fragments.
Conclude that the primary role of topoisomerase at the replication fork is to relieve torsional strain by cutting and rejoining DNA strands, preventing supercoiling and allowing replication to proceed smoothly.
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