Cytosine

Definition

Cytosine is one of the four main nitrogenous bases found in DNA and RNA. It pairs with guanine through three hydrogen bonds.

5 Must Know Facts For Your Next Test

1. Cytosine is a pyrimidine base, meaning it has a single-ring structure.
2. In DNA, cytosine pairs with guanine via three hydrogen bonds, contributing to the stability of the DNA double helix.
3. Cytosine can undergo deamination to form uracil, which is a common type of DNA mutation.
4. In RNA, cytosine also pairs with guanine but is involved in different structural and functional roles compared to DNA.
5. Methylation of cytosine (forming 5-methylcytosine) plays an important role in gene regulation and epigenetic control.

Review Questions

• What type of nitrogenous base is cytosine classified as?
• Which nitrogenous base does cytosine pair with in DNA?
• What happens to cytosine when it undergoes deamination?

Related terms

Guanine:

A purine base that pairs with cytosine through three hydrogen bonds.

Pyrimidines: A class of nitrogenous bases that includes cytosine, thymine, and uracil.

Deamination:

A process where an amino group is removed from a molecule; in cytosine, this converts it into uracil.