Question

If 15% of a DNA sample is made up of thymine, T, what percentage of the sample is made up of cytosine, C?

Answer 1

If 15% are Thymine, and Thymine always pairs with Adenine, then Adenine is also 15%. The remaining bases, amounting to 70% would be equally divided between Cytosine and Guanine, since they always form pairs. So 35% would be the answer.