Which of the following nitrogenous bases are classified as purines?

The classification of nitrogenous bases as purines or pyrimidines is fundamental in understanding the structure of nucleic acids like DNA and RNA. Purines are characterized by their larger, two-ring structure, which distinguishes them from pyrimidines, which have a single ring.

Adenine and Guanine are the two bases classified as purines. Their dual-ring structure is essential for the formation of the nucleotides in nucleic acids, contributing to the overall stability and pairing properties of DNA and RNA. When you consider their roles, adenine pairs with thymine in DNA (or uracil in RNA), and guanine pairs with cytosine. This complementary base pairing is vital for the accurate replication and transcription of genetic material.

Other bases listed, such as cytosine, thymine, and uracil, belong to the pyrimidine category, which have a single-ring structure. Understanding the distinction between purines and pyrimidines is crucial in molecular biology, genetics, and biochemistry, especially when studying the processes of DNA replication and RNA synthesis.