Which statement best describes the structure of a DNA molecule?

• A. A double-stranded helix of antiparallel nucleotide chains held together by complementary base pairing (A with T, and C with G)
• B. A double-stranded molecule in which both strands run in the same direction (parallel) and bases pair A with C and G with T
• C. A single-stranded helix made of amino acids connected by peptide bonds
• D. A triple-stranded helix in which nucleotides are linked by hydrogen bonds along the backbone

Answer: (A)

Verified step by step guidance

1. Recall the basic structure of DNA: DNA is composed of two strands forming a double helix.
2. Understand that the two strands run in opposite directions, which is called antiparallel orientation.
3. Recognize that the strands are held together by complementary base pairing, where adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G).
4. Note that the backbone of each strand is made of sugar and phosphate groups linked by covalent bonds, while the bases pair through hydrogen bonds.
5. Eliminate incorrect options by checking for errors such as parallel strand orientation, incorrect base pairing, presence of amino acids instead of nucleotides, or triple-stranded structures.