How many types of nucleotides are present in DNA?

DNA is composed of four distinct types of nucleotides, each distinguished by its nitrogenous base. The four nucleotides are adenine, thymine, cytosine, and guanine. These bases pair specifically—adenine with thymine and cytosine with guanine—forming the rungs of the DNA double helix structure. The sequence of these nucleotides encodes genetic information, making them essential for the storage and transmission of hereditary traits. Therefore, the presence of four types of nucleotides in DNA is foundational to its structure and function, which is critical for processes such as replication and protein synthesis.