Answer:
Chargaff's rule, also known as the complementary base pairing rule, states that DNA base pairs are always adenine with thymine (A-T) and cytosine with guanine (C-G). A purine always pairs with a pyrimidine and vice versa. However, A doesn't pair with C, despite that being a purine and a pyrimidine.
Step-by-step explanation:
In these nucleotides, there is one of the four possible bases: adenine (A), guanine (G), cytosine (C), or thymine (T) (Figure below). Adenine and guanine are purine bases, and cytosine and thymine are pyrimidine bases. Chemical structure of the four nitrogenous bases in DNA✔✔