Final answer:
The binding of A to T and C to G in DNA is due to the formation of hydrogen bonds between these complementary bases. This base pairing is critical for the double helix structure and the accurate replication and transmission of genetic information.
Step-by-step explanation:
In DNA, adenine (A) always binds to thymine (T), and cytosine (C) always binds to guanine (G). This specificity is due to the shapes and chemical structures of these bases. A and G have a two-ring structure known as purines, while T and C have a single-ring structure known as pyrimidines. The pairing of a two-ring with a one-ring molecule maintains a constant distance between the two DNA strands, ensuring the stability and uniform shape of the DNA double helix.
Hydrogen bonds are responsible for holding these pairs together. Adenine forms two hydrogen bonds with thymine, whereas cytosine forms three hydrogen bonds with guanine. This not only contributes to the double helix's structure but also plays a critical role in the replication and transcription processes of DNA, preserving genetic information across generations.