Question

In a DNA molecule cytosine is 18%. Percentage of adenine would be _________.

• A. 32%
• B. 64%
• C. 36%
• D. 18%

Answer 1

The correct option is A 32%

The answer is option A i.e "32%".
According to Chargraff's rule, Number of purine (adenine+guanine) = Number of pyrimidine (cytosine+thymine).
Hence, the amount of guanine should be equal to cytosine and the amount of adenine should be equal to thymine.
As per the data given above, we can infer that, the percentage of G = the percentage of C = 18%.
Now, total percentage of total A and T = 100 - 18 - 18 = 64, so the percentage of A is 64/2 = 32%.