Which statement best describes the basic structural features of DNA?

Which statement best describes the basic structural features of DNA?

• A. Right-handed double helix with antiparallel strands
• B. Left-handed single helix with parallel strands
• C. Triple helix with identical strands
• D. Circular molecule with no grooves

Answer: (A)

The basic feature being tested is the canonical form of DNA: a right-handed double helix with two sugar-phosphate backbones that run in opposite directions (antiparallel). In this arrangement, bases pair across the interior (A with T, G with C) to stabilize the structure, and the helix presents major and minor grooves that proteins recognize during replication and transcription. The “right-handed” aspect corresponds to the common B-DNA form found in cells, while the strands being antiparallel is crucial for accurate base pairing and the directional synthesis of new DNA strands. The other descriptions—left-handed single helix, triple helix, or circular molecule with no grooves—do not match the standard DNA architecture encountered in most biological contexts.

The basic feature being tested is the canonical form of DNA: a right-handed double helix with two sugar-phosphate backbones that run in opposite directions (antiparallel). In this arrangement, bases pair across the interior (A with T, G with C) to stabilize the structure, and the helix presents major and minor grooves that proteins recognize during replication and transcription. The “right-handed” aspect corresponds to the common B-DNA form found in cells, while the strands being antiparallel is crucial for accurate base pairing and the directional synthesis of new DNA strands. The other descriptions—left-handed single helix, triple helix, or circular molecule with no grooves—do not match the standard DNA architecture encountered in most biological contexts.