Which of the following best describes the structure of a DNA molecule?

• A. A double-stranded, antiparallel helix composed of nucleotide chains with sugar-phosphate backbones and complementary base pairing (A with T, G with C)
• B. A double-stranded, parallel helix composed of amino acids linked by peptide bonds
• C. A single-stranded helical polymer made of ribose sugars and bases that pair A with U and G with C
• D. A triple-stranded helix in which all bases pair identically (A with A, T with T, G with G, C with C)

Answer: (A)