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'''Ribonucleic acid''' (RNA) is a family of biomolecules which perform several essential functions within all cells.  As a type of nucleic acid, RNA is structurally and chemically very similar to [[DNA]]; the two largest differences being that RNA contains ribose instead of 2'-deoxyribose and uses [[uracil]] instead of [[thymine]] as one of its four bases.

'''Ribonucleic acid''' (RNA) is a family of biomolecules which perform several essential functions within all cells.  As a type of nucleic acid, RNA is structurally and chemically very similar to [[DNA]]; the two largest differences being that RNA contains ribose instead of 2'-deoxyribose and uses [[uracil]] instead of [[thymine]] as one of its four bases<ref>Nelson & Cox. (2008). ''Principles of biochemistry''.</ref>.

Unlike DNA, which is primarily used as a template for [[transcription]], RNA molecules perform a diverse set of functions within the cell.  Subsets of RNA are generally classified by their function, which can range from acting as the template for [[translation|protein synthesis]] ("messenger RNA" or "[[mRNA]]") to performing [[ribozyme|enzymatic functions]].  Additionally, many viruses use RNA instead of DNA as their genetic material (e.g. [[retrovirus|retroviruses]]).

Unlike DNA, which is primarily used as a template for [[transcription]], RNA molecules perform a diverse set of functions within the cell.  Subsets of RNA are generally classified by their function, which can range from acting as the template for [[translation|protein synthesis]] ("messenger RNA" or "[[mRNA]]") to performing [[ribozyme|enzymatic functions]].  Additionally, many viruses use RNA instead of DNA as their genetic material (e.g. [[retrovirus|retroviruses]]).

As with DNA, RNAs can exist in single-stranded (annotated "ssRNA") or double-stranded ("dsRNA") forms; however, the vast majority of cellular RNAs are single-stranded.  dsRNAs generally function in post-transcriptional [[gene regulation]] or as viral genetic material.  Targeted degradation of dsRNAs is a major intracellular defence mechanism against viruses.

As with DNA, RNAs can exist in single-stranded (annotated "ssRNA") or double-stranded ("dsRNA") forms; however, the vast majority of cellular RNAs are single-stranded.  dsRNAs generally function in post-transcriptional [[gene regulation]] or as viral genetic material.  Targeted degradation of dsRNAs is a major intracellular defence mechanism against viruses<ref>Alberts et al. (2008). ''Molecular biology of the cell''.</ref><ref>Weaver, Robert F. ''Molecular Biology''. 4th ed. Boston: McGraw-Hill, 2008.</ref>.

==Structure==

==Structure==