If a molecule of DNA contains 10% cytosine, it has guanine and adenine respectively.
A) 40%; 10%
B) 10%; 40%
C) 10%; 80%
D) 10%; 45%
E) 40%; 40%

Question

Quizplus · Accepted Answer

In DNA, cytosine always pairs with guanine, while adenine always pairs with thymine. Therefore, if a molecule of DNA contains 10% cytosine, it also contains 10% adenine (since the amount of adenine and thymine are always equal). This leaves 80% for the other two bases, guanine and thymine. Since guanine always pairs with cytosine, the molecule must also contain 40% guanine. So the answer is B, 10% guanine and 40% adenine.

If a Molecule of DNA Contains 10% Cytosine, It Has