Erwin Chargaff proposed a rule called the Chargaff’s rules which states that in a double-stranded DNA segment, the ratio of purine bases (Adenine+Guanine) and the pyrimidine bases (Cytosine+Thymine) is equal to 1.0 and the number of Adenine is equal to the Thymine and the number of Guanine is equal to the number of Cytosine.

In the given DNA strand, if Cytosine is 18%, then the percentage of Guanine would be 18%, the percentage of Adenine would be 32%, and the percentage of Thymine would be 32%.

A+G=T+C —- 32+18=32+18 where A=T (32% each) and G=C (18% each)