This is used to describe the shape of a DNA molecule.

• A. Single Strand
• B. Triple Helix
• C. Helical Ladder
• D. Double Helix

Answer: (D)

DNA's shape is described as a double helix. This means two long strands wind around each other like a twisted ladder. The sides of the ladder are the sugar-phosphate backbones, and the rungs are pairs of bases that pair specifically (A with T, C with G). This two-stranded, twisting structure helps store genetic information efficiently and provides a reliable template for copying during cell replication. The idea of a single strand would apply to RNA or DNA before strands pair; a triple helix would involve three strands and isn’t the common form of DNA; a “helical ladder” isn’t the standard term used. The double helix best describes both the two-stranded nature and the characteristic twist of DNA.