Describe the structure of DNA.

DNA is made of a string of nucleotide bases attached to one another by a peptide bond. A single nucleotide contains three regions: A phosphate group, a Carboxyl group and a base. Adjacent nucleotides attach to one another by a phosphodiester bond. This forms between the phosphate group of one nucleotide and the sugar group of another. The base groups of the nucleotides are variable, they can be C, G, A, or T.

DNA exists as a double helical structure. Two strands of DNA coil like a spring to form an a-helical structure. The two strands interact via hydrogen bonds. C bases are always opposite G bases and are held by three hydrogen bonds. A bases are always opposite T bases and are held by two hydrogen bonds. The two strands run anti-parallel to one another. This directionality is important for recognition and processing my enzymes.