MTTC Integrated Science (Secondary) (094) Practice Test

What is the function of helicase during DNA replication?

It stabilizes single-stranded DNA. It instigates the denaturation of hydrogen bonds between base pairs. It synthesizes a complementary DNA strand. It seals breaks in the sugar-phosphate backbone.

Correct Answer:

It instigates the denaturation of hydrogen bonds between base pairs.

Explanation:

Opening idea: DNA replication requires opening the double helix so each strand can serve as a template. Helicase does this by breaking the hydrogen bonds between base pairs, using energy from ATP to unwind the DNA and form the replication fork. This unwinding exposes single-stranded templates for DNA polymerases to copy. Stopping or stabilizing the single strands is done by protective proteins, not helicase. The actual synthesis of a new strand is carried out by DNA polymerase, and sealing any backbone breaks is done by DNA ligase.

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