In the above chart, the amount of Adesine=Thymine and Cytosine=Guanine

Erwin Chargaff’s Rules In 1950, Erwin Chargaff analysed the base composition of DNA composition in a number of organisms. He reported that DNA composition varies from one species to another. Such evidence of molecular diversity, which had been presumed absent from DNA, made DNA a more credible candidate for the genetic material than protein. Chargaff's rules Chargaff found that a peculiar regularity in the ratios of nucleotide bases. In the DNA of each species he studies, the number of adenines approximately equaled the number of thymine, and the number of guanines approximately equaled the number of cytosine. In human DNA, for example, the four bases are present in these percentages: A=30.9% and T=29.4%; G=19.9% and C=19.8%. The A=T and G=C equalities, later known as Chargaff's rules, helped Watson and Crick to discover the structure of DNA.   Relating Topics - James Watson and Francis Crick - Overview of the Structure of DNA