Answer: Chargaff discovered two rules while studying bases in the DNA of the organisms. These rules are as follows-
1) In a DNA molecule, total number of adenine is equal to the number of thymine. Similarly, the number of guanine is equal to the number of cytosine. This gave hint about the base pair makeup of the DNA.
2) The amount of these bases that is A, T, C, and G vary from one species to another species. This gave hint about the genetic material of the organism, which is DNA rather than proteins.