A replication bubble is best described as...

A replication bubble is best described as...

• A. A region of DNA damaged by replication stress.
• B. A double-stranded loop that prevents replication.
• C. A region where the DNA is single-stranded due to unwinding.
• D. A bubble formed by RNA primers.

Answer: (C)

When DNA is ready to be copied, helicase unwinds the double helix at the origin, creating a local opening. This opened region exposes single-stranded DNA that serves as the template for DNA polymerases to synthesize new strands. The area of unwinding, where the strands are separated and available for replication, is what a replication bubble refers to. It isn’t about damaged DNA, nor a loop that blocks replication, and it isn’t defined by RNA primers forming the bubble—the primers merely start the synthesis within that open region. The bubble typically contains two replication forks that move outward as replication proceeds, enlarging the single-stranded templates needed for copying both strands.

When DNA is ready to be copied, helicase unwinds the double helix at the origin, creating a local opening. This opened region exposes single-stranded DNA that serves as the template for DNA polymerases to synthesize new strands. The area of unwinding, where the strands are separated and available for replication, is what a replication bubble refers to. It isn’t about damaged DNA, nor a loop that blocks replication, and it isn’t defined by RNA primers forming the bubble—the primers merely start the synthesis within that open region. The bubble typically contains two replication forks that move outward as replication proceeds, enlarging the single-stranded templates needed for copying both strands.