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. 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, and fluorescent in situ hybridization (FISH). Oligonucleotides can also be used for the synthesis a artificial genes.
Oligonucleotides composed of DNA (deoxyoligonucleotides) are often used in the polymerase chain reaction (PCR), a procedure that can be employed to amplify almost any piece of DNA. In this instance, the oligonucleotide is often referred to as a primer, or a short piece of DNA that binds to its complementary target sequence. This generates a place for a polymerase to bind and extend the primer by the addition of nucleotides to make a copy of the target sequence.
Oligonucleotides are often referred to as oligos, in "science slang".
Antisense oligonucleotides are single strands of DNA or RNA that are complementary to a chosen sequence. In the case of antisense RNA they prevent translation of complementary RNA strands by binding to it. Antisense DNA can be used to target a specific, complementary (coding or non-coding) RNA. If binding takes places this DNA/RNA hybrid can be degraded by the enzyme RNase H. Antisense oligonucleotides are being created to use on RNA that eventually produces telomerase, which is active in cancer cells.
One subtype of DNA MicroArrays can be described as substrates (nylon, glass etc.) to which oligonucleotides have been bound at high density. Currently there exist three applications of DNA MicroArrays: polymorphism studies, gene expression studies, and tracking down certain diseases.
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