If a DNA sample were composed of 10% thymine, what would be the percentage of guanine?
A) 10
B) 20
C) 40
D) 80
E) impossible to tell from the information given

Question

Quizplus · Accepted Answer

In DNA, thymine always pairs with adenine, and guanine always pairs with cytosine. This means that if a DNA sample has 10% thymine, it must also have 10% adenine (since the percentages of thymine and adenine are always equal). The remaining 80% is composed of guanine and cytosine. Since adenine and thymine together make up 20%, and there is 10% thymine, there must be 10% adenine. This means that the remaining 80% must be divided evenly between guanine and cytosine, so the percentage of guanine is also 40%. Therefore, the answer is C.

If a DNA Sample Were Composed of 10% Thymine, What