During DNA replication at a replication fork, which DNA strand is synthesized continuously in the same direction as fork movement?

• A. Leading strand
• B. Okazaki fragments
• C. Template strand for the leading strand (parental strand being read $5\prime \to 3\prime$)
• D. Lagging strand

Answer: (A)

Verified step by step guidance

1. Understand the directionality of DNA strands: DNA strands have a 5' to 3' direction and DNA polymerase can only synthesize new DNA in the 5' to 3' direction.
2. Recognize that during replication, the replication fork moves in one direction, unwinding the DNA double helix to expose the template strands.
3. Identify that the leading strand is synthesized continuously because its template strand runs in the 3' to 5' direction, allowing DNA polymerase to add nucleotides in the same direction as the replication fork movement.
4. Know that the lagging strand is synthesized discontinuously in short segments called Okazaki fragments because its template strand runs 5' to 3', opposite to the fork movement, requiring synthesis in the opposite direction in fragments.
5. Conclude that the strand synthesized continuously in the same direction as the replication fork movement is the leading strand.