One of two types of nitrogenous bases found in nucleotides, characterized by a six-membered ring fused to a five-membered ring. Adenine (A) and guanine (G) True / False.

True

Explanation:

Adenine and Guanine fall under the category of Purine nitrogenous base. Purine is made of six member pyrimidine ring fused to five member imidazole ring. It is water soluble in nature.

A purine always pairs with a pyrimidine base to form a DNA base pair. Thymine and Cytosine are the two pyrimidine bases. Adenine bonds with Thymine by forming two hydrogen bonds and Guanine is bonded to Cytosine via three hydrogen bonds. When a purine base is formed it self inhibits formation of more purine and also activates formation of pyrimidine base. Hence, amount of purine and pyrimidine are almost equal in cell.