Definition for Pyrimidine
From Biology Forums Dictionary
1) The bases cytosine (C), thymine (T), and uracil (U) with a single ring.
2) In organic chemistry, pyrimidine is an aromatic, nitrogen-containing six-membered ring compound.
In biochemistry, pyrimidine is understood usually as a generic term for heterocyclic bases - components of nucleotides and nucleic acids - that contain the pyrimidine structure as a nucleus (compare with purines). Thus, the three pyrimidine bases shown in the figure - cytosine (2-oxo, 4-amino pyrimidine), uracil (2,4-dioxopyrimidine), and thymine (2,4-dioxo-5-methylpyrimidine or 5-methyluracil) - are the standard pyrimidine bases found in DNA and RNA. Thymine is usually limited to DNA, while in RNA uracil takes the place of thymine.
