Cytosine molecule. Computer artwork showing the structure of a molecule of the nucleobase cytosine (2-oxy-4-aminopyrimidine). Atoms are shown as colour-coded spheres: carbon (green), hydrogen (white), nitrogen (blue) and oxygen (red), with the bonds between them as rods. Cytosine is one of the bases found in DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). The positioning of these bases along the RNA and DNA chains is known as the genetic code. Each genetic code is unique and gives organisms their individual characteristics.