In a Certain Species of Animal, 33% of the Bases

Question

In a certain species of animal, 33% of the bases in its DNA are A. What percent of the bases are C?
A) 8.5%
B) 17%
C) 33%
D) 34%

Accepted Answer

In DNA, there are four types of bases: adenine (A), cytosine (C), guanine (G), and thymine (T). Since the total percentage of bases must add up to 100%, and 33% of the bases are A, then the remaining 67% must be the other three bases combined (G, C, and T). If we assume that G and T are evenly distributed, then the percentage of C must be 1/3 of the remaining 67%, which is approximately 22.33%. Rounded to the nearest whole number, the answer is 17%. Therefore, the best choice is B.