cytosín

Cytosine is one of the four main nucleobases found in DNA and RNA. It is a pyrimidine derivative, meaning it has a heterocyclic aromatic organic compound with two nitrogen atoms at positions 1 and 3 of the six-member ring. Cytosine is represented by the letter C and plays a crucial role in the genetic code.

In DNA, cytosine always pairs with guanine through three hydrogen bonds. This specific base pairing is fundamental to the double helix structure of DNA and is essential for DNA replication and transcription. In RNA, cytosine also pairs with guanine.

Cytosine can undergo deamination, a chemical reaction where an amino group is removed. This process can convert cytosine into uracil, another pyrimidine nucleobase. If this deamination occurs in DNA and is not repaired, it can lead to mutations. For this reason, methylated cytosine, where a methyl group is added to cytosine, is a significant epigenetic modification that can affect gene expression without altering the DNA sequence itself. This epigenetic marking is particularly important in cellular differentiation and development.