Which is the correct base pairing found in a normal DNA molecule?

In a normal DNA molecule, the double helix structure is stabilized by complementary base pairing between nitrogenous bases on opposite strands. According to the Watson-Crick model, adenine (A), a purine, specifically pairs with thymine (T), a pyrimidine, through two hydrogen bonds [1]. Similarly, guanine (G) pairs with cytosine (C) through three hydrogen bonds [1]. This specific pairing ensures a uniform diameter of the DNA molecule and is the basis for Chargaff's rules, where the amount of adenine equals thymine and guanine equals cytosine. While adenine pairs with uracil in RNA, in the context of a normal DNA molecule, adenine only pairs with thymine [1]. Therefore, among the given options, only the pairing of Adenine with Thymine is correct.

Sources

1. [1] https://www.sciencedirect.com/topics/immunology-and-microbiology/base-pairing