Question

Which one of the following ratio is constant in DNA of a species :

• A. A+T/G + C
• B. A+G/T+C
• C. A+C/T+G
• D. A+U/T+G

Answer 1

Answer: (A)

Chargaff discovered that in DNA
(1) Purines and pyrimidines occur in equal amounts.
(2) Phosphate and deoxyribose sugar occur in equal number.
(3) Molar amount of adenine is equal to that of thymine and cytosine equal to guanine.
(4) Base ratio $A+T/G+C$ is specific for a species. It is rarely one. The ratio is high in advanced organisms and low in primitive organisms, Chargaff's rule is applicable only to DNA and not RNA.