Oligonucleotide

n. short chain of up to 20 nucleotides

Oligonucleotides are short sequences of nucleotides (RNA or DNA), typically with twenty or fewer bases. Automated synthesizers allow the synthesis of oligonucleotides up to 160 to 200 bases. The length of a synthesized base is usually denoted by 'mer' (from 'Greek' meros "part"). For example, a fragment of 25 bases would be called a 25-mer. Oligonucleotides are often used as probes for detecting complementary DNA or RNA because they bind readily to their complements. Examples of procedures that use oligonucleotides are DNA microarrays, Southern blots, fluorescent in situ hybridization (FISH), and the synthesis of artificial genes.
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A short DNA molecule composed of relatively few nucleotide bases.

A short, synthetic DNA string used as a probe (as in SSOP) or primer (as in SSP) in molecular genetic studies.