During DNA replication, which event occurs at the origins of replication?

During DNA replication, which event occurs at the origins of replication?

• A. The two strands are separated
• B. The RNA primers are added
• C. The nucleotides are degraded
• D. The histones are removed

Answer: (A)

Opening the DNA at the origin is what starts replication: helicase unwinds the double helix and the two strands separate, creating replication forks. This separation is the essential first step that makes the template strands accessible for copying. After the strands are split, RNA primers are laid down on each template to provide starting points for DNA polymerase, but the defining event at the origin itself is the separation of the two strands. Nucleotides aren’t degraded as part of initiation, and histone removal is part of broader chromatin remodeling rather than the specific origin event.

Opening the DNA at the origin is what starts replication: helicase unwinds the double helix and the two strands separate, creating replication forks. This separation is the essential first step that makes the template strands accessible for copying. After the strands are split, RNA primers are laid down on each template to provide starting points for DNA polymerase, but the defining event at the origin itself is the separation of the two strands. Nucleotides aren’t degraded as part of initiation, and histone removal is part of broader chromatin remodeling rather than the specific origin event.