Question

Adenine is 30% then what would be the % of guanine:

• A. 20%
• B. 10%
• C. 30%
• D. 40%

Answer 1

The correct option is A 20%

A purine always forms a bond with pyrimidine. Thus, there will always be equal numbers of purines and pyrimidines in a nucleotide.
Adenine(A) forms a bond with thymine(T) or uracil(U) and guanine(G) forms a bond with cytosine(C).
If there is 30% of adenine then equal amounts of thymine or uracil should be present. Thus the adenine - uracil/thymine pair will constitute for 60%, the remaining 40% is divided equally between guanine and cytosine. Thus, there will be 20% of guanine.

A=T=U=30%, therefore A+T=60%.
Now, G=C, therefore G+C=(100-60)=40%. So, G=20%.