Question

The base composition in DNA isolated from cow liver cells is 28% adenine; what percent of the bases are cytosine?

A) 14%
B) 22%
C) 28%
D) 36%
E) 56%

Answer 1

In DNA, adenine pairs with thymine, forming a complementary base pair. Therefore, the percentage of adenine is equal to the percentage of thymine. Since adenine is 28%, thymine is also 28%.

The remaining two bases are cytosine and guanine, and they form another complementary pair. So, the percentage of cytosine is the same as the percentage of guanine.

Since adenine (and thymine) is 28%, the total percentage for cytosine (and guanine) is 100% - 28% = 72%.

Therefore, the percentage of cytosine is 36% (half of 72%).

So, the correct answer is:

D) 36%