Genetic information is stored in DNA as combinatorial codes held in nucleosides and nucleotides, in which form it is passed from parents to their offspring. Analogs of nucleosides and nucleotides are used clinically as medicinal agents such as reverse transcriptase inhibitors. Therefore, the preparation and development of these species as effective, selective and nontoxic antiviral and antitumor agents has been the subject of intense research.1)
In addition to this, the development of Polymerase Chain Reaction (PCR) methodology has brought a dramatic change and rapid development in studies of DNA. At the current time the draft version in decoding and mapping human genome has been almost completed, and the functional analyses of genome and analyses of “Single Nucleotide Polymorphism” (SNP) are being vigorously pursued. Discovery of the RNAi process has facilitated the fast progression of studies of RNA. At the same time, chemically synthesized oligoDNA and oligoRNA have been studied as potential antisense DNAs, siRNAs and DNA aptamers; as oligonucleotide therapeutic agents, primers for PCR method, and elements of DNA computers.