<P> Nucleic acids then are polymeric macromolecules assembled from nucleotides , the monomer - units of nucleic acids . The purine bases adenine and guanine and pyrimidine base cytosine occur in both DNA and RNA , while the pyrimidine bases thymine ( in DNA ) and uracil ( in RNA ) in just one . Adenine forms a base pair with thymine with two hydrogen bonds , while guanine pairs with cytosine with three hydrogen bonds . </P>
the genetic code is contained within the nucleotide sequences of what type of organic molecule
polymeric macromolecules