Thirty percent of the bases in a sample of DNA extracted from eukaryotic cells are adenine.What percentage of the bases are cytosine in this DNA?
A) 10
B) 20
C) 30
D) 40
E) 50

Question

Quizplus · Accepted Answer

According to Chargaff's rules, in DNA, the amount of adenine (A) is equal to thymine (T), and the amount of guanine (G) is equal to cytosine (C). If 30% of the bases are adenine, then 30% are also thymine, making a total of 60% for A and T together. This leaves 40% for G and C together. Since G and C are present in equal amounts, cytosine makes up 20% of the bases.

Thirty Percent of the Bases in a Sample of DNA