ABSTRACT
Nucleic acids are polymers of nucleotides or in short polynucleotides. Similar to amino acids in proteins, it is the nucleotide sequence that determines the final structure, function, and information content of nucleic acids. This chapter deals with a chemical and geometric view on the constituents of nucleic acids, their assembly into secondary and tertiary structures, and finish with a brief description on the interconversion of DNA topoisomers and the folding of RNA. The number of canonic building blocks that make up nucleic acids is smaller than for proteins: just four nucleobases compared to the twenty standard amino acids. These nucleobases are: adenine; guanine; cytosine; and thymine. RNA contains uracil (U) instead of T. RNA shows much more variation of nucleobases than DNA due to a large variety of post-transcriptional modifications. Several more radically modified nucleobases are specific for particular tRNAs. The tertiary structure of tRNA explains many principles of how RNA molecules fold.
