In replication, the leading strand is synthesized in which direction?

In replication, the leading strand is synthesized in which direction?

• A. 5' to 3' on the growing strand toward the replication fork
• B. 3' to 5' on the growing strand toward the replication fork
• C. 5' to 3' on the template strand
• D. 3' to 5' on the template strand

Answer: (A)

DNA polymerase can only add nucleotides to the 3' end, so synthesis proceeds in the 5' to 3' direction. For the leading strand, the template runs 3' to 5' toward the fork, allowing the polymerase to move toward the fork while continuously laying down new nucleotides. Therefore, the growing strand extends in the 5' to 3' direction toward the replication fork. This continuous synthesis contrasts with the lagging strand, which must be synthesized in short fragments away from the fork due to its opposite template orientation.

DNA polymerase can only add nucleotides to the 3' end, so synthesis proceeds in the 5' to 3' direction. For the leading strand, the template runs 3' to 5' toward the fork, allowing the polymerase to move toward the fork while continuously laying down new nucleotides. Therefore, the growing strand extends in the 5' to 3' direction toward the replication fork. This continuous synthesis contrasts with the lagging strand, which must be synthesized in short fragments away from the fork due to its opposite template orientation.