The rule that in a DNA the amount of adenine equals to that of the thymine and that guanine equals to that of cytosine is known as

Chargaff worked on chemical components of DNA and put forward certain generalisations like Purines and pyramidines occur in equal amounts. Purines of DNA are adenine and guanine, Pyrimidines of DNA are thymine and cytosine, A+G =T+C, Purine of adenine is equimolar with pyrimidine thymine, purine guanine is equimolar with pyrimidine cytosine.