Definition

A molecule that is the basic building block of the nucleic acids DNA and RNA. A nucleotide is made up of a nitrogen-containing base (adenine, guanine, thymine, and cytosine in DNA, and adenine, guanine, uracil, and cytosine in RNA), a phosphate group, and a sugar molecule (deoxyribose in DNA, and ribose in RNA). DNA and RNA are polymers made up of many nucleotides.