Oligonucleotide

Synonymous of oligonucleotid are: oligomer, oligo, N-mer (where N is a number, e.g. 22-mer)

Oligonucleotides are short chains of synthetic deoxyribose nucleic acid (DNA). They are usually around 20-30 nucleotides and can be formed by bond cleavage of longer segment us by vitro synthesis from the 3’ end to the 5’ end. Automated synthesizers allow the synthesis of oligonucleotides up to 200 bases. The synthesis is performed in a column carrying the first nucleotide in the 3´end of the synthesized sequence. In subsequent steps, other nucleotides are bound behind the first nucleotide according to the desired sequence defined by an operator of the synthesizer. Structure of an oligonucleotide do not contain a phosphate group either on 5' end or 3' end. Regarding phosphate groups, oligos are like natural DNA but unlike DNA fragments generated by enzymatic digestion with restriction endonucleases.

Sequence of oligonucleotide is recorded by Adenin, Guanin, Cytosin, and Thymin. Example of oligonucleotide sequence:

5' AAG TCC GAT GCA GGC CCC GTA G 3'

The sequence of oligonucleotide is composed of nucleotides (syn.: bases). The length of an oligonucleotide is expressed by the number of nucleotides.Example:

Oligonucleotide AAG TCC GAT GCA GGC CCC GTA G is 22 nucleotides long     or
Oligonucleotide AAG TCC GAT GCA GGC CCC GTA G is 22-mer