Which base pairs with adenine in DNA?

Adenine pairs with thymine in DNA due to the specific base-pairing rules that govern the formation of the double helix structure of DNA. In this pairing, adenine, which is a purine, forms two hydrogen bonds with thymine, which is a pyrimidine. This fit is essential for the stability of the DNA molecule and ensures the accurate replication and transmission of genetic information.

The pairing occurs because of the presence of a nitrogenous base on each nucleotide. Adenine contains an amine group that complements thymine's carbonyl and amine groups, creating a stable connection that supports the overall structure of DNA. This specificity also contributes to the mechanism of complementary base pairing, which is critical during DNA replication and transcription processes.