Uracil ( /ˈjʊərəsɪl/) one of the four nucleobases in the nucleic acid of RNA that are represented by the letters A, G, C and U. The others are adenine, cytosine, and guanine. In RNA, uracil (U) binds to adenine (A) via two hydrogen bonds. In DNA, the uracil nucleobase is replaced by thymine.
Uracil is a common and naturally occurring pyrimidine derivative. Originally discovered in 1900, it was isolated by hydrolysis of yeast nuclein that was found in bovine thymus and spleen, herring sperm, and wheat germ. It is a planar, unsaturated compound that has the ability to absorb light.
Studies reported in 2008, based on 12C/13C isotopic ratios of organic compounds found in the Murchison meteorite, suggested that uracil, xanthine and related molecules were formed extraterrestrially.
In 2012 an analysis of data from the Cassini mission orbiting in the Saturn system showed that Titan's surface composition may include uracil.
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