Question

Which of the following are the purine nucleotides?

• A. Adenine and cytosine
• B. Cytosine and thymine
• C. Adenine and guanine
• D. Guanine and thymine

Answer 1

The correct option is C Adenine and guanine

Nitrogenous bases
Nitrogenous bases are basic compounds composed of heterocyclic aromatic rings formed of carbon and nitrogen. Based on the structure of the rings, nitrogenous bases can be of two types - purines and pyrimidines.

Purine
Purines are adenine and guanine. Their structure is formed of two rings, one hexagonal pyrimidine ring and an imidazole ring with 5 arms.

Pyrimidine
Pyrimidines are cytosine, thymine and uracil. Their structure is formed of a single heterocyclic ring having 4 carbon and 2 nitrogen atoms.

Final answer
(D) Adenine and guanine