question_answer

The nucleic acid the purine base having two possible binding sites is

A)  thymine        

B)  cytosine

C)  guanine        

D)  adenine

Correct Answer: D

Solution :

Thymine (pyrimidine base) and adenine (purine base) attach to each other by two H-bonds while cytosine (pyrimidine) and guanine (purine) attach by three H-bonds.