How are oligos made?

Oligos are made using a DNA synthesizer, which is basically a computer-controlled reagent delivery system. The first base is attached to a solid support, usually a glass or polystyrene bead, which is designed to anchor the growing DNA chain in the reaction column. DNA synthesis consists of a series of chemical reactions.

Each cycle of reactions results in the addition of a single DNA base. A chain of DNA bases can be built by repeating the synthesis cycles until the desired length is achieved.