Editing Sequencing (section)

==RNA sequencing==
[[RNA]] is less stable in the cell, and also more prone to nuclease attack experimentally. As RNA is generated by [[Transcription (genetics)|transcription]] from DNA, the information is already present in the cell's DNA. However, it is sometimes desirable to [[RNA-Seq|sequence RNA]] molecules. While sequencing DNA gives a genetic profile of an organism, sequencing RNA reflects only the sequences that are actively [[gene expression|expressed]] in the cells. To sequence RNA, the usual method is first to [[reverse transcriptase|reverse transcribe]] the RNA extracted from the sample to generate cDNA fragments. This can then be sequenced as described above.
The bulk of RNA expressed in cells are [[ribosomal RNA]]s or [[small RNA]]s, detrimental for cellular translation, but often not the focus of a study. This fraction can be removed ''in vitro'', however, to enrich for the messenger RNA, also included, that usually <u>is</u> of interest. Derived from the [[exon]]s these mRNAs are to be later [[translation|translated]] to [[protein]]s that support particular cellular functions. The [[expression profile]] therefore indicates cellular activity, particularly desired in the studies of diseases, cellular behaviour, responses to reagents or stimuli. [[eukaryote|Eukaryotic]] RNA molecules are not necessarily [[co-linear]] with their DNA template, as [[intron]]s are excised. This gives a certain complexity to map the read sequences back to the genome and thereby identify their origin.
For more information on the capabilities of next-generation sequencing applied to whole [[transcriptome]]s see: [[RNA-Seq]] and [[MicroRNA Sequencing]].