Which statement correctly describes DNA structure and base pairing?

Which statement correctly describes DNA structure and base pairing?

• A. DNA is a double-stranded molecule; cytosine pairs with thymine; adenine pairs with guanine
• B. DNA is double-stranded; cytosine pairs with guanine, adenine with thymine
• C. DNA is single-stranded; cytosine pairs with adenine
• D. DNA is triple helix; base pairing not defined

Answer: (B)

DNA is a double-stranded molecule with complementary base pairing: adenine pairs with thymine and cytosine pairs with guanine. This pairing is highly specific and each strand serves as a template for the other, giving the two strands their complementary sequences and enabling accurate replication. The correct statement captures both the double-stranded nature and the precise A–T and C–G pairings. The other descriptions misstate the pairing or the structure: one suggests incorrect base pairs, another claims single-stranded DNA, and another mentions a triple helix with no defined base pairing.

DNA is a double-stranded molecule with complementary base pairing: adenine pairs with thymine and cytosine pairs with guanine. This pairing is highly specific and each strand serves as a template for the other, giving the two strands their complementary sequences and enabling accurate replication. The correct statement captures both the double-stranded nature and the precise A–T and C–G pairings.

The other descriptions misstate the pairing or the structure: one suggests incorrect base pairs, another claims single-stranded DNA, and another mentions a triple helix with no defined base pairing.