Antiparallel orientation in DNA refers to what characteristic of the two strands during replication?

Antiparallel orientation in DNA refers to what characteristic of the two strands during replication?

• A. The strands run in same directions
• B. The sugars face opposite directions
• C. The bases pair across the helix
• D. The two strands run in opposite directions

Answer: (D)

Antiparallel orientation means the two DNA strands run in opposite directions. One strand runs in the 5' to 3' direction and the other in the 3' to 5' direction, relative to the overall layout of the molecule. This opposite directionality is why DNA replication proceeds with polymerases adding nucleotides only to the 3' end, producing a leading strand continuously toward the fork and a lagging strand in short Okazaki fragments on the other side. While bases pair across the helix and the backbone has opposite ends, the key point of antiparallel orientation is the opposite directional runs of the two strands.

Antiparallel orientation means the two DNA strands run in opposite directions. One strand runs in the 5' to 3' direction and the other in the 3' to 5' direction, relative to the overall layout of the molecule. This opposite directionality is why DNA replication proceeds with polymerases adding nucleotides only to the 3' end, producing a leading strand continuously toward the fork and a lagging strand in short Okazaki fragments on the other side. While bases pair across the helix and the backbone has opposite ends, the key point of antiparallel orientation is the opposite directional runs of the two strands.