Nucleic acid bases are essential components of DNA and RNA, consisting of five primary types: adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U).

These bases serve as the fundamental building blocks of nucleic acids. Among them, adenine and guanine are classified as purine bases, while cytosine, thymine, and uracil are categorized as pyrimidine bases.

In DNA, the base pairing occurs as follows: adenine pairs with thymine, and guanine pairs with cytosine. This complementary pairing is vital for forming the base pairs that stabilize the double helical structure of DNA. In RNA, however, uracil takes the place of thymine and pairs with adenine.

The specific sequence of nucleic acid bases in both DNA and RNA encodes the genetic information of an organism. Alterations in this sequence, known as mutations, can result in genetic disorders and various diseases.

Furthermore, nucleic acid bases play critical roles in several cellular processes, including DNA replication, transcription, and translation. They are indispensable for the proper functioning of cells and for the transmission of genetic information from one generation to the next.

In summary, nucleic acid bases are the fundamental units of DNA and RNA, significantly influencing genetic information and the various cellular processes that sustain all living organisms.