According to Chargaff’s base pairing rules, if 15% of the DNA sample is made up of thymine, what percentage of the sample is made up of cytosine?

Answer 1

According to Chargaff's base pairing rules, the amount of adenine is equal to thymine, and the amount of guanine is equal to cytosine.

Since thymine makes up 15% of the DNA sample, adenine also makes up 15% of the sample (as they pair together).

Since adenine and guanine together make up 30% of the DNA sample (15% adenine + 15% thymine), the remaining 70% of the sample is made up of cytosine and guanine.

Since adenine and guanine must be equal in amount, each of them makes up half of the remaining 70%, which is 35%.

Therefore, cytosine makes up 35% of the DNA sample.