A nucleotide is composed of 3 main parts: The base (A,T,G,C), a ribose sugar, and a phosphate group. The base can be split into 2 categories: purines and pyrimidines. Purines consist of Adenine and Guanine, while pyrimidines concept of Cytosine, Thymine, and Uracil.
Deoxyribonucleic acid (DNA) is the hereditary matter in cells that makes up the repository for genes. DNA's structure consists of sugar, phosphate groups,and nitrogenous bases in its nucleotides. These bases are cytosine, thymine, adenine, and guanine. Cytosine and thymine are classified as pyrimidines that have a single ring. Adenine and guanine are classified as purines that have a double rings. Adenine base pairs with thymine (uracil only in RNA), and cytosine base pairs with guanine.