Cytosine

Definition

Cytosine is one of the four main bases found in DNA and RNA. It pairs with guanine.

Related terms

Thymine:

A nucleobase that pairs with adenine in DNA but gets replaced by uracil when transcribing into RNA.

Pyrimidine: The category of nitrogenous bases that includes cytosine along with thymine (in DNA) or uracil (in RNA).

Complementary Base Pairing Rule: The rule stating that certain nitrogenous bases are always paired together - such as cytosines always pairing up with guanines.