RNA Polymerase and DNA Helix Opening — NEET Biology
✅ Asked in NEET 2020Name the enzyme that facilitates opening of DNA helix during transcription: (NEET 2020)
Name the enzyme that facilitates opening of DNA helix during transcription: (NEET 2020)
Answer & NCERT explanation
Correct answer: B — RNA polymerase
RNA polymerase itself facilitates DNA helix opening during transcription. It has helicase activity that unwinds the double helix at the transcription bubble. Unlike DNA replication where separate helicase enzymes are needed, RNA polymerase combines both helicase and polymerase functions. DNA helicase is primarily involved in replication, not transcription.
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It somehow also facilitates opening of the helix and continues elongation. Only a short stretch of RNA remains bound to the enzyme. Once the polymerases reaches the terminator region, the nascent RNA falls off, so also the RNA polymerase. This results in termination of transcription.
RNA polymerase doesn't just synthesize RNA—it actively unwinds the DNA double helix during transcription. Students often think the helix opens automatically or that only complementarity matters, missing the enzyme's mechanical role. The polymerase creates a transcription bubble, holding the template strand in place while the complementary RNA strand forms. Remember: the enzyme facilitates helix opening AND elongation simultaneously. Once transcription reaches the terminator region, the nascent RNA detaches, followed by polymerase release. This concept is crucial because NEET tests understanding of the transcription mechanism beyond simple base pairing—it requires knowing the dynamic structural changes during the process.
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