Oligonucleotides are short DNA or RNA molecules typically 10-25 nucleotides in length. They can exist as either single-stranded or double-stranded polymers of nucleic acid polymers. In research, oligonucleotides are frequently used as probes to detect specific sequences of complementary DNA or RNA.

Common applications that use oligonucleotides include:

• Sequencing
• PCR
• Fluorescence in situ hybridization (FISH)
• Southern Blots
• DNA microarrays
• Drug discovery