Solid-phase synthesis of nucleic acids. The oligonucleotide is synthesized in the 3′→5′ direction, starting with a single nucleotide that is covalently attached to a solid support, such as a glass bead (Si). In a repeated series of chemical reactions, nucleotides protected by the dimethoxytrityl (DMT) group from unwanted reactions are sequentially deprotected and reacted to produce a new phosphodiester linkage.