What shape is DNA?

• A. Double Helix
• B. Single Strand
• C. Circular
• D. Linear Chain

Answer: (A)

DNA is shaped as a double helix: two long strands wind around each other to form a spiral ladder. The sugar–phosphate backbones run on the outside, while the bases pair up inside the ladder (A with T, G with C) through hydrogen bonds, holding the two strands together. The strands run in opposite directions (antiparallel), which is important for accurate replication and transcription. This helical structure explains why genetic information is stored in a stable, compact form and how it can be accurately copied.

A single strand wouldn’t provide the complementary base pairing that makes replication possible. A circular shape describes some molecules (like certain plasmids) but not the common, ladder-like form of DNA. A linear chain describes a stretched-out appearance or a chromosome segment, but not the characteristic double-helix structure.