Nucleic acids are polymers formed by attaching together monomers called nucleotides. There are two important nucleic acids, DNA, which is the genetic material, and RNA, which is involved in using the genetic information. Nucleotides consist of a phosphate, a 5-carbon sugar, and a nitrogenous base. There are 4 kinds of nitrogenous bases in DNA. These fall into two classes, purines and pyrimidines. The purine bases are referred to as A and G and the pyrimidines as T and C. In RNA there is a U base instead of the T.