Which enzyme unwinds the DNA double helix during replication?
Answer and explanation
Correct answer: A. Helicase
- Step 1: Initiation of DNA replication requires separating complementary antiparallel parental strands to expose template sequences.
- Step 2: DNA helicase breaks the hydrogen bonds between complementary base pairs at the replication origin, unwinding the double helix and advancing the replication fork.
- Step 3: Single-stranded DNA-binding proteins stabilize the unwound strands, while topoisomerase relieves torsional supercoiling.
Answer
Helicase.
Why not the others: DNA ligase seals phosphodiester nicks in the sugar-phosphate backbone between adjacent DNA fragments; Primase synthesizes short complementary RNA primers required to initiate polymerase activity; DNA polymerase synthesizes nascent DNA strands by adding deoxynucleotides complementary to the template.
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