Nucleobases

Uracil /ˈjʊərəsɪl/ (U) is one of the four nucleobases in the nucleic acid of RNA that are represented by the letters A, G, C and U.

Thymine /ˈθaɪmᵻn/ (T, Thy) is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T.

Cytosine (/ˈsaɪtəˌsiːn, -ˌziːn, -ˌsɪn/; C) is one of the four main bases found in DNA and RNA, along with adenine, guanine, and thymine (uracil in RNA).

5-Hydroxymethylcytosine is a DNA pyrimidine nitrogen base.

Fluorouracil (5-FU) (trade name Adrucil among others) is a medication which is used in the treatment of cancer.

Adenine /ˈædᵻnᵻn/ (A, Ade) is a nucleobase (a purine derivative).

Guanine /ˈɡwɑːnᵻn/ (G, Gua) is one of the four main nucleobases found in the nucleic acids DNA and RNA, the others being adenine, cytosine, and thymine (uracil in RNA).

Isocytosine or 2-aminouracil is a pyrimidine base that is an isomer of cytosine.

2,4-Diaminopyrimidine is a diaminopyrimidine.

2-Aminopurine, an analog of guanine and adenine, is a fluorescent molecular marker used in nucleic acid research.

5-Hydroxyuracil is an oxidized form of cytosine that is produced by the oxidative deamination of cytosines by reactive oxygen species.

5-Hydroxycytosine is an oxidized form of cytosine that is associated with an increased frequency of C to T transition mutations, with some C to G transversions.

5-Bromouracil (or 5-bromo-2,4(1H,3H)-pyrimidinedione or 5-BrU or 5-BU) is a brominated derivative of uracil that acts as an antimetabolite or base analog, substituting for thymine in DNA, and can induce DNA mutation in the same way as 2-aminopurine.

Flucytosine, also known as 5-fluorocytosine (5-FC), is an antifungal medication.

5-Methylcytosine is a methylated form of the DNA base cytosine that may be involved in the regulation of gene transcription.

2,6-Diaminopurine is a compound used to treat leukemia.

Dihydrouracil is an intermediate in the catabolism of uracil.

β-D-Glucopyranosyloxymethyluracil or base J is a hypermodified nucleobase found in the DNA of kinetoplastids including the human pathogenic trypanosomes.

Queuine (Q) is a hypermodified nucleobase found in the first (or wobble) position of the anticodon of tRNAs specific for Asn, Asp, His, and Tyr, in most eukaryotes and prokaryotes.

6-O-Methylguanine is a derivative of the nucleobase guanine in which a methyl group is attached to the oxygen atom.

Isoguanine or 2-hydroxyadenine is a purine base that is an isomer of guanine.