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Q.
If a double stranded $DNA$ has $20\%$ of cytosine, what will be the percentage of adenine in it?
Molecular Basis of Inheritance
Solution:
According to Chargaff's rule, the amount of adenine is always equal to that of thymine and the amount of guanine is always equal to that of cytosine, i.e., $A=T$ and $G = C$. Also, the purines and pyrimidines are always in equal amounts, i.e., $A + G = T + C$. Now, given $dsDNA$ has $20\%$ cytosine and hence guanine will be also $20\%$.
So, $A + T$ must be $60\%$. Therefore, percentage of adenine would be $60/2 = 30\%$.