Multiple Choice
During DNA replication, what is the primary function of topoisomerase (e.g., DNA gyrase in bacteria) ahead of the replication fork?
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8. DNA Replication
Overview of DNA Replication
Multiple Choice
In the overview of DNA replication, what is the primary function of helicase?
A
It adds nucleotides to the growing DNA strand in the direction.
B
It unwinds the DNA double helix by breaking hydrogen bonds to separate the two strands at the replication fork.
C
It synthesizes short RNA primers needed to initiate DNA synthesis.
D
It seals nicks between Okazaki fragments by forming phosphodiester bonds.
Verified step by step guidance1
Understand that DNA replication involves multiple enzymes, each with a specific role to ensure accurate copying of the genetic material.
Identify the role of helicase: it is responsible for unwinding the DNA double helix, which means it breaks the hydrogen bonds between complementary base pairs to separate the two strands.
Recognize that this unwinding creates the replication fork, a Y-shaped region where the DNA strands are separated and replication can proceed.
Distinguish helicase's function from other enzymes: DNA polymerase adds nucleotides, primase synthesizes RNA primers, and ligase seals nicks between Okazaki fragments.
Conclude that the primary function of helicase is to unwind the DNA double helix by breaking hydrogen bonds, enabling the replication machinery to access single-stranded DNA templates.
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