Question:
Given below are two statements, one is labelled as Assertion (A) and other labelled as Reason (R).
Assertion (A): The enzyme helicase is required for DNA replication.
Reason (R): Helicase unwinds the double-stranded DNA molecule by breaking the hydrogen bonds between the base pairs.
In light of the above statements, choose the correct answer from the options given below:
Given below are two statements, one is labelled as Assertion (A) and other labelled as Reason (R).
Assertion (A): The enzyme helicase is required for DNA replication.
Reason (R): Helicase unwinds the double-stranded DNA molecule by breaking the hydrogen bonds between the base pairs.
In light of the above statements, choose the correct answer from the options given below:
Assertion (A): The enzyme helicase is required for DNA replication.
Reason (R): Helicase unwinds the double-stranded DNA molecule by breaking the hydrogen bonds between the base pairs.
In light of the above statements, choose the correct answer from the options given below:
Show Hint
DNA helicase acts as a molecular zipper, consuming ATP to break the hydrogen bonds between base pairs and unwind the double helix ahead of the replication fork.
Updated On: Jul 31, 2026
- Both (A) and (R) are true and (R) is the correct explanation of (A).
- Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
- (A) is true but (R) is false.
- (A) is false but (R) is true.
Show Solution
Verified By Collegedunia
The Correct Option is A
Solution and Explanation
Step 1: Understanding the Concept:
DNA replication is a highly coordinated process that requires separating the two complementary strands of the double helix to expose single-stranded templates for DNA polymerases.
This strand separation is performed by specialized motor proteins called helicases.
Step 2: Detailed Explanation:
Let us analyze both statements:
- Assertion (A) is true: The enzyme DNA helicase is essential for DNA replication.
Without helicase, the stable double-stranded DNA molecule cannot be opened, preventing the replication machinery from accessing the template strands.
- Reason (R) is true: Helicase binds to double-stranded DNA at the replication origin and moves along the phosphodiester backbone.
Using energy derived from ATP hydrolysis, helicase physically disrupts and breaks the hydrogen bonds holding the complementary base pairs together (Adenine-Thymine and Guanine-Cytosine).
This enzymatic separation unwinds the double helix, creating a replication fork with single-stranded templates.
Since the unwinding of the double helix by breaking hydrogen bonds is exactly *why* helicase is required for DNA replication, Reason (R) is correct and is the correct explanation of Assertion (A).
Step 3: Final Answer:
Hence, the correct option is (A).
DNA replication is a highly coordinated process that requires separating the two complementary strands of the double helix to expose single-stranded templates for DNA polymerases.
This strand separation is performed by specialized motor proteins called helicases.
Step 2: Detailed Explanation:
Let us analyze both statements:
- Assertion (A) is true: The enzyme DNA helicase is essential for DNA replication.
Without helicase, the stable double-stranded DNA molecule cannot be opened, preventing the replication machinery from accessing the template strands.
- Reason (R) is true: Helicase binds to double-stranded DNA at the replication origin and moves along the phosphodiester backbone.
Using energy derived from ATP hydrolysis, helicase physically disrupts and breaks the hydrogen bonds holding the complementary base pairs together (Adenine-Thymine and Guanine-Cytosine).
This enzymatic separation unwinds the double helix, creating a replication fork with single-stranded templates.
Since the unwinding of the double helix by breaking hydrogen bonds is exactly *why* helicase is required for DNA replication, Reason (R) is correct and is the correct explanation of Assertion (A).
Step 3: Final Answer:
Hence, the correct option is (A).
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