What does cytosine pair with in DNA?

In DNA, cytosine pairs with guanine through the formation of three hydrogen bonds, creating a stable base pairing that is essential for the structure of the DNA double helix. This pairing is consistent with Chargaff's rules, which state that in any given DNA molecule, the amount of adenine approximately equals the amount of thymine, and the amount of cytosine approximately equals the amount of guanine. This complementary base pairing is crucial for accurate DNA replication and the maintenance of genetic information during cell division.

Other bases, such as adenine and thymine, form a pair, whereas uracil is found in RNA rather than DNA, where it pairs with adenine instead of thymine. Guanine’s specific bonding with cytosine is fundamental to both the structure and function of DNA.