Which of the following statements correctly describes the difference between the leading and the lagging strands of DNA during DNA replication?

• A. The leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.
• B. The leading strand is synthesized by adding nucleotides to the 3' end of the growing strand, and the lagging strand is synthesized by adding nucleotides to the 5' end.
• C. The lagging strand is synthesized continuously, whereas the leading strand is synthesized in short fragments that are ultimately stitched together.
• D. The leading strand is synthesized at twice the rate of the lagging strand.

Answer: (A)

Verified step by step guidance

1. Understand the concept of DNA replication: DNA replication is the process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules. It involves the unwinding of the double helix and the synthesis of new strands.
2. Identify the role of the replication fork: The replication fork is the area where the DNA double helix is unwound to allow for replication. It moves along the DNA, creating two single strands that serve as templates for new DNA synthesis.
3. Differentiate between the leading and lagging strands: The leading strand is synthesized continuously in the same direction as the replication fork movement, while the lagging strand is synthesized in short fragments called Okazaki fragments in the opposite direction.
4. Clarify the direction of synthesis: DNA polymerase adds nucleotides to the 3' end of the growing strand. Therefore, both the leading and lagging strands are synthesized by adding nucleotides to the 3' end, not the 5' end.
5. Recognize the synthesis rate: The synthesis rate of the leading and lagging strands is not inherently different; both strands are synthesized simultaneously, but the lagging strand requires additional steps to join the Okazaki fragments.