Which statement correctly describes the synthesis of the leading strand during DNA replication?

• A. Leading strand is synthesized discontinuously toward the fork.
• B. Leading strand is synthesized continuously toward the fork.
• C. Lagging strand is synthesized continuously toward the fork.
• D. Lagging strand is synthesized discontinuously away from the fork.

Answer: (B)

DNA polymerases can only add nucleotides to the 3' end, so new DNA grows in the 5' to 3' direction. At the replication fork, the template strand that runs 3' to 5' toward the fork allows a single, continuous synthesis of the new strand as the fork opens. That leading strand is built in one long piece moving toward the fork. The other template runs 5' to 3' toward the fork, which means its new strand cannot be made in one piece; it’s synthesized in short segments (Okazaki fragments) away from the fork and later joined. So the leading strand is synthesized continuously toward the fork.