What are oligonucleotides?

Oligonucleotides, also known as oligos, are short single-stranded DNA or RNA molecules that readily bind to their respective complementary oligonucleotides. Oligos could be found either in nature or synthesized in laboratory. One typical example of natural oligos is microRNA, who usually contains about 22 nucleotides and has important functions in RNA silencing and regulation of gene expression. Synthetic oligos, usually made by solid-phase chemical synthesis, are commonly used in research nowadays. A wide range of applications have been found for synthetic oligos from genetic testing to forensic research and next-generation sequencing.