Which statement best describes the progression of replication from origins?

Which statement best describes the progression of replication from origins?

• A. Replication stops at the origin.
• B. Replication proceeds in both directions from origins.
• C. Replication occurs only on leading strand.
• D. Replication requires RNA primers to begin on both strands.

Answer: (B)

From the starting point, replication moves in two directions. When an origin fires, the double helix is opened by helicase, creating two replication forks that race away from the origin in opposite directions. DNA polymerases then synthesize new DNA in the 5' to 3' direction on both forks. One strand (the leading strand) is built continuously toward the fork, while the other strand (the lagging strand) is built discontinuously as Okazaki fragments on the far side of each fork. This bidirectional progression from the origin is why replication proceeds in both directions. The other statements don’t fit: replication doesn’t stop at the origin, replication includes both strands (not just the leading), and while primers are needed to start synthesis, the key point is the outward bidirectional movement from the origin.

From the starting point, replication moves in two directions. When an origin fires, the double helix is opened by helicase, creating two replication forks that race away from the origin in opposite directions. DNA polymerases then synthesize new DNA in the 5' to 3' direction on both forks. One strand (the leading strand) is built continuously toward the fork, while the other strand (the lagging strand) is built discontinuously as Okazaki fragments on the far side of each fork. This bidirectional progression from the origin is why replication proceeds in both directions. The other statements don’t fit: replication doesn’t stop at the origin, replication includes both strands (not just the leading), and while primers are needed to start synthesis, the key point is the outward bidirectional movement from the origin.