According to the Watson-Crick double-helix model of DNA, how many hydrogen bonds form between complementary guanine and cytosine nitrogenous bases?
Answer and explanation
Correct answer: D. Three hydrogen bonds
- Step 1: Guanine and cytosine pair specifically through three hydrogen bonds (G===C). Step 2. This makes GC-rich DNA duplexes more thermally stable than AT-rich sequences, which pair with two hydrogen bonds. Answer: Three hydrogen bonds. Why not the others: Two bonds connect adenine and thymine (A==T); four and one do not occur in canonical Watson-Crick base pairs.
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