What describes DNA orientation between its two strands?

What describes DNA orientation between its two strands?

• A. Their subunits run in opposite directions
• B. They run in the same direction
• C. They have identical sequences
• D. They are not complementary

Answer: (A)

DNA is organized as two strands that run in opposite directions along the backbone, an arrangement called antiparallel. This means one strand runs 5' to 3' while the other runs 3' to 5'. Bases pair specifically (A with T, G with C), so the strands are complementary, not identical. This antiparallel setup is essential for replication because DNA polymerases add nucleotides to the 3' end and must read the template strand in the opposite direction, enabling coordinated copying of both strands. If the strands ran in the same direction, or if they weren’t complementary, proper base pairing and polymerase function would be compromised.

DNA is organized as two strands that run in opposite directions along the backbone, an arrangement called antiparallel. This means one strand runs 5' to 3' while the other runs 3' to 5'. Bases pair specifically (A with T, G with C), so the strands are complementary, not identical. This antiparallel setup is essential for replication because DNA polymerases add nucleotides to the 3' end and must read the template strand in the opposite direction, enabling coordinated copying of both strands. If the strands ran in the same direction, or if they weren’t complementary, proper base pairing and polymerase function would be compromised.