What is the difference between leading and lagging strand synthesis?

What is the difference between leading and lagging strand synthesis?

• A. The leading strand is made continuously toward the fork, while the lagging strand is made in short fragments away from the fork.
• B. Both are synthesized in the same direction.
• C. Leading is discontinuous, lagging is continuous.
• D. Lagging strand is synthesized toward the fork in one piece.

Answer: (A)

DNA polymerases can only add nucleotides in the 5' to 3' direction, and the two template strands at the replication fork are antiparallel. This arrangement means the leading strand template runs in the same general direction as the fork is opening, so the polymerase can lay down a long, continuous strand toward the fork. The lagging strand template runs opposite to the fork movement, so a long, uninterrupted chain isn’t possible; instead, synthesis happens in short segments called Okazaki fragments that are made away from the fork, each starting with an RNA primer and then extended until it meets the previous fragment. These fragments are later joined by DNA ligase to form a continuous strand. So the difference is continuous synthesis toward the fork on the leading strand versus discontinuous synthesis in fragments away from the fork on the lagging strand.

DNA polymerases can only add nucleotides in the 5' to 3' direction, and the two template strands at the replication fork are antiparallel. This arrangement means the leading strand template runs in the same general direction as the fork is opening, so the polymerase can lay down a long, continuous strand toward the fork. The lagging strand template runs opposite to the fork movement, so a long, uninterrupted chain isn’t possible; instead, synthesis happens in short segments called Okazaki fragments that are made away from the fork, each starting with an RNA primer and then extended until it meets the previous fragment. These fragments are later joined by DNA ligase to form a continuous strand. So the difference is continuous synthesis toward the fork on the leading strand versus discontinuous synthesis in fragments away from the fork on the lagging strand.