Which statement accurately describes the leading strand?

• A. The leading strand is synthesized in short segments called Okazaki fragments
• B. The lagging strand is synthesized continuously toward the fork
• C. The leading strand is synthesized toward the fork
• D. The lagging strand is a template for RNA synthesis

Answer: (C)

The main idea is how DNA polymerase works in a 5' to 3' direction and how replication creates a continuous leading strand versus a discontinuous lagging strand. Because polymerase can only add nucleotides to a free 3' end, new DNA grows in the 5' to 3' direction toward the replication fork on the leading strand. The template for this strand runs 3' to 5' relative to the fork, so synthesis can proceed smoothly in one piece toward the fork. The other strand, the lagging strand, must be synthesized in short segments because its template runs opposite to the direction of fork movement. Each segment, or Okazaki fragment, is started with a short RNA primer and then extended in the 5' to 3' direction away from the fork, with later joining to form a continuous strand. The lagging strand isn’t a template for RNA synthesis; RNA primers are made on the DNA template to initiate each fragment, not to create the lagging strand itself.