Final answer:
According to Chargaff's rules, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C) due to specific hydrogen bond patterns in DNA.
Step-by-step explanation:
According to Chargaff's data, adenine (A) must pair with thymine (T), and guanine (G) must pair with cytosine (C). Chargaff's rules, based on his research findings, indicate that the amount of A equals the amount of T, and the amount of C equals the amount of G in DNA.
These base pairings are due to the specific hydrogen bonding patterns, where A pairs with T through two hydrogen bonds, and G pairs with C through three hydrogen bonds. This complementary base-pairing helps in preserving the genetic information during cell division and is a fundamental principle in the structure of DNA.