uracili

Uracil, in some contexts referred to as uracili, is a pyrimidine nucleobase that forms part of RNA. It pairs with adenine via two hydrogen bonds, helping to encode genetic information and participate in transcription and translation. In DNA, uracil is normally absent and is replaced by thymine, so uracil is not a standard DNA base.

Chemically, uracil has the formula C4H4N2O2 and consists of a six-membered ring with two carbonyl groups at the 2- and 4- positions, classifying it as pyrimidine-2,4-dione. It is a small, polar molecule that is soluble in water and participates in hydrogen bonding within RNA strands.

Biosynthesis and metabolism: Uracil is produced and used in cells through pyrimidine metabolism. In de novo synthesis, uracil is formed as part of the pathway that yields uridine monophosphate (UMP) and other RNA nucleotides. Some organisms salvage uracil to UMP via uracil phosphoribosyltransferase. In DNA, cytosine deamination can generate uracil, which is repaired by specialized glycosylases to maintain genomic integrity.

Medical and research relevance: Uracil is a component of certain chemotherapeutic agents, notably fluoropyrimidines such as 5-fluorouracil, which interfere with nucleotide synthesis and RNA processing. In molecular biology, uracil is used in various techniques and as a basis for synthesizing uracil-containing nucleic acids and for certain sequencing approaches.

See also: Nucleobases; RNA; DNA; Thymine.