During the initiation of DNA replication, what happens to the DNA strands?

During the initiation of DNA replication, what happens to the DNA strands?

• A. DNA unwinds and strands separate, facilitated by Topoisomerase and Helicase.
• B. DNA is replicated by RNA polymerase.
• C. Nucleotides are degraded by nucleases.
• D. The double helix remains fully paired until synthesis begins.

Answer: (A)

During initiation, the double-stranded DNA must open so each strand can serve as a template for copying. Helicase uses energy to break hydrogen bonds and unwind the helix, creating the replication fork. Topoisomerase relieves the twisting strain that builds up as the strands separate, helping to prevent knots and tangling. As a result, the two strands separate and become single-stranded templates for DNA polymerases to synthesize new DNA. The other statements don’t fit because replication is carried out by DNA polymerase, not RNA polymerase (which functions in transcription). Nucleases degrade nucleic acids rather than initiating replication. And the double helix does not stay fully paired—the unwinding is essential to expose bases for synthesis.

During initiation, the double-stranded DNA must open so each strand can serve as a template for copying. Helicase uses energy to break hydrogen bonds and unwind the helix, creating the replication fork. Topoisomerase relieves the twisting strain that builds up as the strands separate, helping to prevent knots and tangling. As a result, the two strands separate and become single-stranded templates for DNA polymerases to synthesize new DNA.

The other statements don’t fit because replication is carried out by DNA polymerase, not RNA polymerase (which functions in transcription). Nucleases degrade nucleic acids rather than initiating replication. And the double helix does not stay fully paired—the unwinding is essential to expose bases for synthesis.