Are Adenine and Thymine Equal?

Think of a strand of DNA. Each base pairs with a specific partner, allowing us to determine their percentages: adenine and thymine are always equal, and cytosine and guanine are always equal.

Why are adenine and thymine not equal?

The amount of adenine is not always equal to the amount of thymine because adenine is found in DNA and RNA while thymine is only found in DNA.

What is the ratio of adenine to thymine?

Chargaff's rules state that DNA from any species of any organism should have a 1:1 stoichiometric ratio of purine and pyrimidine bases (i.e., A+G=T+C) and, more specifically, that the amount of guanine should be equal to cytosine and the amount of adenine should be equal to thymine.