cytosine

[ sahy-tuh-seen, -zeen, -sin ]

noun

, Biochemistry.

1. a pyrimidine base, C 4 H 5 N 3 O, that is one of the fundamental components of DNA and RNA, in which it forms a base pair with guanine. : C

cytosine

/ ˈsaɪtəsɪn /

noun

1. a white crystalline pyrimidine occurring in nucleic acids; 6-amino-2-hydroxy pyrimidine. Formula: C 4 H 5 N 3 O See also DNA RNA

cytosine

/ sī′tə-sēn′ /

1. A pyrimidine base that is a component of DNA and RNA, forming a base pair with guanine. Chemical formula: C 4 H 5 N 3 O.

Word History and Origins

Origin of cytosine¹

< German Cytosin (1894); cyto-, -ose ², -ine ²

Example Sentences

Nucleotides are composed of three distinctive parts: a sugar molecule, a phosphate group and one of the four nucleobases adenine, thymine, guanine and cytosine.

From Science Daily

For example, exposure to water can cause a chemical reaction called deamination that changes the nucleotide cytosine such that it appears to be the nucleotide thymine upon analysis.

From Scientific American

One loose end, Sasselov acknowledges, is that RAO has only been shown to lead to the synthesis of two of RNA’s four nucleotides, cytosine and uracil.

From Science Magazine

Huntington’s is a hereditary neurodegenerative disease caused by excess repetitions of three building blocks of DNA — cytosine, adenine, and guanine — on a gene called huntingtin.

From New York Times

Rather than inducing random changes in the virus’ RNA genome, the drug is more likely to cause specific nucleic acid substitutions, with guanine switching to adenine and cytosine to uracil.

From Science Magazine