One of two nucleic acids which transmit genetic information in all living organisms. It is a polymer composed of a phosphate backbone, ribose sugar residues and one of the following bases: Uridine, Adenine, Guanosine, Cytosine. Modifications of some of the bases is also observed, e.g. inosine, pseudouridine. Compare deoxyribonucleic acid (DNA).
Once thought of as passive carriers of information, RNA is capable of catalytic activity, either as as part of the ribosome (rRNA) or alone as ribozymes.
In mammals the main subtypes include:
- Messenger RNA (mRNA) which starts life as heterogenous nuclear RNA (hnRNA) or precursor mRNA
- Transfer RNA (tRNA)
However, there are several other types of RNA have roles in other various cellular pathways (see Wikipedia:Non-coding RNA) and RNA interference. Noncoding RNAs (ncRNA) are also involved in epigenetic regulation such as with the HOTAIR genes (hox transcript antisense RNA non-protein coding) indirect effects on chromatin.
- Efference RNA (perhaps also termed intron miRNA)
- Micro RNA (miRNA)
- pri-miRNA - the direct transcription from a gene coding for a miRNA
- Evidence exists that likely to be able to influence phenotype in vertebrates meaning that ncRNA DNA may have to be considered in phenotype expression
- Pre-microRNA (pre-miRNA)
- Promoter RNA (pRNA)
- Ribosomal RNA (rRNA)
- Signal recognition particle RNA (4.5S RNA)
- Small interfering RNA (siRNA)
- Short hairpin RNA (shRNA)
- Small nuclear RNA (snRNA)
- Small nucleolar RNA (snoRNA)
RNA viruses also exist.
Methods of Detection
RNA is often very labile and sensitive to degradation by ubiquitous RNases. Traditionally detected with Northern blotting, but it is often easier to convert RNA into more stable DNA with reverse transcriptase and then analyse with standard DNA tools.