(1) The purines and pyrimidines are always in equal amount, A+G=C+T.
(2) The amount of adenine is equal to thymine, and the amount of cytosine is equal to guanine., A=T, G=C.
(3) The base ratio A+T/G+C may vary from one species to another but it will remain constant for a given species. He proposed that the these ratios can be used to identify the species and classify them.
(4) The deoxyribose sugar and phosphate components occur in equal proportions.

Figure 26.7: Packing of purine and pyrimidine in DNA double helix.