<< Back to glossary index


The molecules that serve as the building blocks of DNA and RNA. Nucleotides consist of one nitrogenous baseadenine, cytosine, guanine, or thymine (uracil in RNA), a sugar (deoxyribose in DNA, ribose in RNA) and a phosphate group.

Use in clinical context

A triplet of three nucleotides within protein-coding sections of the genome encode for an amino acid. Changes to the nucleotide sequence can impact which amino acid is coded for and alter the form and function of the resulting protein. When it is noted that DNA consists of 3 billion letters or a single letter change in person’s DNA is the cause of a condition, this is a reference to the nitrogenous base within each nucleotide.

Last updated on 31st May, 2019