Mostly there's a chart follow the chart and see the varible
Explanation:
There are four nitrogenous bases<span> found in </span>DNA<span> that are called guanine, adenine, thymine and cytosine.</span>They<span> are abbreviated by the first letter in their name, or G, A, T and C. The </span>bases<span> can be divided into two categories: Thymine and cytosine are called pyrimidines, and adenine and guanine are called purines.</span>