Question
Biology Question on the molecular basis of inheritance
If the total amount of adenine and thymine in a double-stranded DNA is 60%, the amount of guanine in this DNA will be
A
0.15
B
0.2
C
0.3
D
0.4
Answer
0.2
Explanation
Solution
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%