Final answer:
Chargaff's base pairing rules state that in DNA, adenine (A) always pairs with thymine (T), and guanine (G) pairs with cytosine (C), maintaining a consistent ratio of A=T and G=C within a species.
Step-by-step explanation:
Chargaff's base pairing rules revealed that adenine (A) always equals the amount of thymine (T) while guanine (G) always equals the amount of cytosine (C).
Chargaff, an Austrian biochemist, found variations in the amounts of adenine, thymine, guanine, and cytosine across different species; however, within a species, the ratio of adenine to thymine and cytosine to guanine was consistent. This observation is critical as it led to the understanding of complementary base pairs in the DNA structure.
Adenine forms two hydrogen bonds with thymine, and guanine forms three hydrogen bonds with cytosine. This pairing is essential for the stability of the DNA helix and ensures the correct transfer of genetic information during cell division.