How many hydrogen bonds form between guanine and cytosine in DNA?

• A. 2 hydrogen bonds
• B. 3 hydrogen bonds
• C. 4 hydrogen bonds
• D. 1 hydrogen bond

Answer: (B)

Guanine and cytosine, two of the four nucleotide bases in DNA, are paired together through hydrogen bonds that play a critical role in stabilizing the DNA double helix structure. Specifically, guanine forms three hydrogen bonds with cytosine. These bonds involve specific interactions between the nitrogen and oxygen atoms in the bases, which facilitate the strong and consistent pairing necessary for the integrity of the DNA molecule.

This triadic bond formation is significant in comparison to the pairing of adenine with thymine, which only forms two hydrogen bonds. The three hydrogen bonds between guanine and cytosine contribute to a more stable DNA structure, making this pairing more robust than others within the double helix. Such stability is important in biological processes such as DNA replication and transcription, where the integrity of base pairing is essential.