Chimeric RNA And Oligonucleotides

Chimeric RNA And Oligonucleotides

Ribonucleic acid (RNA) is a nucleic acid and consists of a long chain of nucleotide units. Each nucleotide consists of a nitrogenous base, a ribose sugar, and a phosphate. RNA is very similar to DNA, but differs in a few important structural details: in the cell RNA is usually single stranded, while DNA is usually double stranded. RNA nucleotides contain ribose while DNA contains deoxyribose (a type of ribose that lacks one oxygen atom), and RNA has the base uracil rather than thymine which is present in DNA.

Antisense RNA

Antisense RNA (aRNA) is single-stranded RNA that is complementary to a messenger RNA (mRNA) strand transcribed within a cell. Antisense RNA may be introduced into a cell to inhibit translation of a complementary mRNA by base pairing to it and physically obstructing the translation machinery. This effect is therefore stoichiometric. An example of naturally occurring mRNA antisense mechanism is the hok/sok system of the E.coli R1 plasmid. Antisense RNA has long been thought of as a promising technique for disease therapy; the only such case to have reached the market is the drug fomivirsen. Generally, antisense RNA still lack effective design, biological activity, and efficient route of administration.

Oligonucleotide

Oligonucleotide is a short segment of RNA or DNA, typically with twenty or fewer bases. Although they can be formed by cleavage of longer segments, they are now more commonly synthesized by polymerizing individual nucleotide precursors. Automated synthesizers allow the synthesis of oligonucleotides up to 160 to 200 bases. The length of the oligonucleotide 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 DNA or RNA because they bind readily to their complements. Examples of procedures that use oligonucleotides include DNA microarrays, Southern blots, ASO analysis, fluorescent in situ hybridization (FISH), and the synthesis of artificial genes.