Non-coding RNA

As a "non-coding" (understand "protein-non-coding") RNA (ncRNA), we denote all functional RNA molecules that are not translated into protein during the translation process. In general, they belong into two categories, distinguishable by size:
 * Less than 200 nucleotides
 * Longer than 200 nucleotides

RNA less than 200 nucleotides
This group includes, for example:
 * Transfer RNA (tRNA) — RNA involved in the translation process. We distinguish 49 types / families of tRNA. In the nuclear genome, there are 497 genes for tRNA (many of which are on chromosomes 1 and 6), transcribed by RNA polymerase III (another 22 tRNA is coded by the mitochondrial genome).
 * Ribosomal RNA (rRNA) – forming part of ribosomes, there are 4 different types – 5S rRNA, 18S rRNA, 5,8S rRNA and 28S rRNA
 * Small Nuclear RNA (snRNA) – is involved in the process of so-called splicing – processing of hnRNA, splitting of introns
 * Small nucleolar RNA (snoRNA) – plays an important role in the synthesis and maturation (post-transcription chemical modification) of rRNA, snRNA and tRNA. A cluster of snoRNA in the 15q chromosome area leads to a manifestation of Prader-Willi syndrome.
 * A number of regulatory types of RNA such as:
 * microRNA – involved in the regulation of gene expression – are complementary and bound to certain parts of mRNA, thus regulating their translation
 * Small interfering RNA (siRNA)
 * piRNA (piwi-interacting RNA) – RNA that interacts with PIWI family proteins.

RNA longer than 200 nucleotides
This group bears the common name long non-coding RNA (lncRNA). Probably the best-known representative of lncRNA is the XIST gene (X Inactivation Specific Transcript; Xq13.2; OMIM: ) applied in the X-chromosome inactivation process.

Related articles

 * RNA