Question

If a species contains 40% guanine in its DNA, what is the percentage of cytosine that is would contain?

Options

• 60

• 40

• 27

• 30

Answer 1

40

Explanation:

According to Chargaff’s Rule, in any double-stranded DNA molecule, the amount of guanine (G) is always equal to the amount of cytosine (C) because they are complementary base pairs held together by triple hydrogen bonds. Therefore, if a species contains 40% guanine, it must also contain exactly 40% cytosine to maintain this 1 : 1 ratio. The remaining 20% of the DNA would be split equally between adenine (10%) and thymine (10%).