- Cytosine (C) is one of four chemical bases in DNA, the other three being adenine (A), guanine (G), and thymine (T). Within the DNA molecule, cytosine bases located on one strand form chemical bonds with guanine bases on the opposite strand. The sequence of four DNA bases encodes the cell's genetic instructions.
Definition from: Talking Glossary of Genetic Terms from the National Human Genome Research Institute
- A pyrimidine base (C4H5N3O) that codes genetic information in the polynucleotide chain of DNA or RNA.
Definition from: Merriam-Webster's Medical Dictionary by Merriam-Webster Inc.
Related discussion in the Handbook
See also Understanding Medical Terminology.