Which compounds are classified as pyrimidines?

Pyrimidines are a specific category of nitrogenous bases that play a critical role in the composition of nucleic acids, such as DNA and RNA. The correct classification of pyrimidines includes cytosine, thymine, and uracil. Each of these compounds features a single six-membered ring, which distinguishes them from purines, another category of nitrogenous bases that have a two-ring structure, such as adenine and guanine.

Cytosine and thymine are found in DNA, with uracil replacing thymine in RNA. This fundamental difference between pyrimidines and purines underlines their distinct structural characteristics and functional roles in genetic information storage and transfer. Understanding this classification is essential for studying the nature of nucleic acids and their biological significance.