nucleotide nu·cle·o·tide (nōō'klē-ə-tīd', nyōō'-)
Any of various compounds consisting of a nucleoside combined with a phosphate group and forming the basic constituent of DNA and RNA.
The molecules that form the basic modular structure of the double helix of the DNA molecule. A nucleotide consists of three molecules — a sugar, a phosphate group, and a molecule called a base. If the double helix is a twisted ladder, the sugar and phosphates form the sides of the ladder and pairs of bases form the rungs. There are four different bases, usually abbreviated A, C, G, and T for adenine, cytosine, guanine, and thymine). The order of bases in DNA determines the genetic code.