Q. If the total amount of adenine and thymine in a double-stranded DNA is 60%, then the amount of guanine in this DNA will be
A) 15%
B) 20%
C) 30%
D) 40%
Explanation
Purine and pyrimidine nitrogenous base are found in DNA. Among purines, adenine pairs only with the pyrimidine thymine. Similarly, guanine pairs with the cytosine. The fact that total amount of purine will be equal to total amount of pyrimidine was first enunciated by Chargaff in 1950. From this law, Adenine=Thymine=60/2=30% Guanine=Cytosine=40/2=20%
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.