How many hydrogen bonds connect an Adenine-Thymine (A-T) base pair (Hard) compared to a Guanine-Cytosine (G-C) pair in DNA?
Answer and explanation
Correct answer: C. A-T has 2 hydrogen bonds, whereas G-C has 3 hydrogen bonds
- Step 1: In Watson-Crick double helix, complementary base pairing is mediated by hydrogen bonds. Step 2. Adenine and Thymine form 2 hydrogen bonds (N-H...O and N-H...N), while Guanine and Cytosine form 3 hydrogen bonds, making GC-rich DNA thermally more stable. Answer: A-T has 2 hydrogen bonds, whereas G-C has 3 hydrogen bonds. Why not the others: Reversing counts contradicts Watson-Crick pairing; equal counts ignores third GC bond; both having 3 is chemically false.
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