Pyrimidine

Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions one and three of the six-member ring. Heterocyclic compounds are organic compounds that contain a ring structure containing atoms in addition to carbon such as sulfur, oxygen or nitrogen as part of the ring.

Pyrimidines is also used in reference to pyrimidine derivatives and structurally related forms. Pyrimidine is very similar to pyridine, but has an extra nitrogen atom. Pyrimidine is isomeric with two other forms of diazine.

All organisms pass on their heredity via the genetic material that is based upon nucleic acids, and every living cell utilizes these pyrimidine nucleobases for transmitting and storing the information needed for manufacturing proteins.

In DNA and RNA, pyrimidines (actually derivatives) cytosine, thymine, and uracil form hydrogen bonds with their complementary purines.

In DNA, the purines adenine (A) and guanine (G) pair up with the pyrimidines thymine (T) and cytosine (C) respectively.

In RNA, the complement of adenine is uracil instead of thymine and thus the pairs that form are adenine: uracil and guanine and cytosine.

Source from: Wikipedia