Which one is correct with respect to nitrogenous bases?

Adenine= Purine; Uracil= Pyrimidine.

The correct answer is Option (3)- Adenine= Purine; Uracil= Pyrimidine.

Nucleic acids are composed of a combination of 5 nitrogenous bases:

• Guanine and adenine are double-ringed purine molecules
• Cytosine, thymine and uracil are single-ringed pyrimidine molecules

Thymine and uracil are chemically similar molecules – thymine is present in DNA, while uracil is used in RNA.

 Complementary Base Pairing

The nitrogenous bases may form hydrogen bonds according to complementary base pairing:

• Adenine always forms two hydrogen bonds with thymine / uracil
• Guanine always forms three hydrogen bonds with cytosine