cytosine

noun

cy·​to·​sine ˈsī-tə-ˌsēn 

: a pyrimidine base C₄H₅N₃O that codes genetic information in the polynucleotide chain of DNA or RNA compare adenine, guanine, thymine, uracil

Examples of cytosine in a Sentence

Recent Examples on the Web

Most consumer clocks are built on DNA methylation, a process in which chemical tags called methyl groups attach to DNA as a person ages, altering the cytosine base and creating a pattern that correlates with biological age. — Hanna Wickes, Miami Herald, 14 Sep. 2026

The bases form pairs, with guanine always binding with cytosine and adenine always binding with thymine. — Jeremy Kahn, Fortune, 8 Sep. 2026

The system used here involves a protein that chemically lops off a nitrogen from the base cytosine (C), converting it to something that base-pairs more like thymidine (T). — ArsTechnica, 9 Apr. 2026

Scientists have discovered that a sample of the Ryugu asteroid collected by Japan's Hayabusa 2 spacecraft contains the nucleobases adenine, guanine, cytosine, thymine and uracil, the building blocks of DNA and RNA upon which all life is based. — Robert Lea, Space.com, 17 Mar. 2026

Word History

Etymology

International Scientific Vocabulary cyt- + -ose + -ine entry 2

First Known Use

1894, in the meaning defined above

Rhymes for cytosine

• acini
• aldine
• amine
• arsine
• carinii
• cosine
• delphine
• domine
• latine
• ovine
• pennine
• porcine

Kids Definition

cytosine

noun

cy·​to·​sine ˈsīt-ə-ˌsēn 

: a chemical base that is a pyrimidine and codes genetic information in DNA and RNA compare adenine, guanine, thymine, uracil

Medical Definition

cytosine

noun

cy·​to·​sine ˈsīt-ə-ˌsēn 

: a pyrimidine base C₄H₅N₃O that codes genetic information in the polynucleotide chain of DNA or RNA compare adenine, guanine, thymine, uracil