In DNA, there are four distinct types of nucleotides, each characterized by a different nitrogenous base. The four types are adenine (A), thymine (T), cytosine (C), and guanine (G). Each nucleotide is composed of a phosphate group, a sugar molecule (deoxyribose in the case of DNA), and one of these nitrogenous bases.
The specific arrangement of these four nucleotides encodes genetic information, allowing for the complex processes of replication and transcription. The unique pairing of the bases (adenine with thymine and cytosine with guanine) is essential for the complementary structure of the DNA double helix. This combination of four nucleotides is fundamental to genetic diversity and the functioning of all living organisms.
While there are other nucleotides involved in cellular processes (such as those found in RNA or used in energy transfer, like ATP), pertaining specifically to DNA, only the four nucleotides mentioned are present.