If 20 percent of the bases in a sample of double-stranded DNA is adenine, what percentage of the bases would be cytosine?
A) 15
B) 30
C) 70
D) 35
E) 40

Question

Quizplus · Accepted Answer

In double-stranded DNA, adenine always pairs with thymine, and cytosine always pairs with guanine. Therefore, if 20% of the bases are adenine, then 20% of the bases must also be thymine. This means that the remaining 60% of the bases must be cytosine and guanine. Since cytosine and guanine are present in equal amounts, 30% of the bases must be cytosine.

If 20 Percent of the Bases in a Sample of Double-Stranded