Question

Which among the following is the exact ratio of guanine to cytosine in a DNA double helical structure?

• A. 3:2
• B. 2:1
• C. 1:3
• D. 1:1

Answer 1

Answer:

D. 1:1

The ratio of the purines (adenine and guanine) to the pyrimidine (thymine and cytosine) should always be equal to 1:1. This is in accordance to the Chargaff’s rule. The ratio of 1:1 is also based on the base pair rule.