How many hydrogen bonds are formed between an A:T base pair?

An A:T base pair in DNA is held together by two hydrogen bonds. This specific pairing occurs because adenine (A) can form two hydrogen bonds with thymine (T). The first hydrogen bond typically forms between the amino group of adenine and the carbonyl oxygen of thymine, while the second hydrogen bond forms between an amine group on adenine and the hydrogen on a nitrogen in thymine.

The two hydrogen bonds are crucial for stabilizing the double helix structure of DNA, allowing it to maintain its integrity while also providing the necessary flexibility for the strands to separate during processes like DNA replication and transcription. In contrast, a G:C pair forms three hydrogen bonds, which contributes to the overall strength of regions in DNA where these pairs are located. Understanding the specific number of hydrogen bonds in different base pairings is fundamental in molecular biology, particularly in the context of DNA structure and function.