what is the function of the non-coding ones?
Silencing of blocks of chromatin via recruitment of Polycomb complex so that messenger RNA could not be transcribed from them
Long non-coding RNAs
Next to be linked to regulation were Xist and other long noncoding RNAs associated with X chromosome inactivation.  Their roles, at first mysterious, were shown by Jeannie T. Lee and others to be the silencing of blocks of chromatin via recruitment of Polycomb complex so that messenger RNA could not be transcribed from them.  Additional lncRNAs, currently defined as RNAs of more than 200 base pairs that do not appear to have coding potential, have been found associated with regulation of stem cell pluripotency and cell division.
rna consists of how many chains of subunits Small RNAs mainly include 5.8S ribosomal RNA (rRNA), 5S rRNA, transfer RNA (tRNA), microRNA (miRNA), small interfering RNA (siRNA), small nucleolar RNA (snoRNAs), Piwi-interacting RNA (piRNA), tRNA-derived small RNA (tsRNA) and small rDNA-derived RNA (srRNA) are they also double-stranded? Yes, Double-stranded RNA is RNA with two complementary strands how is it different from dna? Analysis of mRNA, tRNA, rRNA, snRNAs, and other non-coding RNAs  has revealed that self-complementary sequences that allow parts of the RNA to fold and pair with itself to form double helices and they are highly structured. Unlike DNA, their structures do not consist of long double helices, but rather collections of short helices packed together into structures akin to proteins
Many of the newly identified ncRNAs have not been validated for their function. It is also likely that many ncRNAs are non functional. To silence of blocks of chromatin via recruitment of Polycomb complex so that messenger RNA could not be transcribed from them. Many of the conserved, essential and abundant ncRNAs are involved in translation.
Non-coding RNA RNA Non-coding RNA
Introduction Long non-coding RNAs In translation
The number of non-coding RNAs within the human genome is unknown; however, recent transcriptomic and bioinformatic studies suggest that there are thousands of them. Many of the newly identified ncRNAs have not been validated for their function. It is also likely that many ncRNAs are non functional (sometimes referred to as junk RNA), and are the product of spurious transcription. Their roles, at first mysterious, were shown by Jeannie T. Lee and others to be the silencing of blocks of chromatin via recruitment of Polycomb complex so that messenger RNA could not be transcribed from them.  Additional lncRNAs, currently defined as RNAs of more than 200 base pairs that do not appear to have coding potential, have been found a Many of the conserved, essential and abundant ncRNAs are involved in translation. 
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RNA [SEP] Long non-coding RNAs
Next to be linked to regulation were Xist and other long noncoding RNAs associated with X chromosome inactivation. Their roles, at first mysterious, were shown by Jeannie T. Lee and others to be the silencing of blocks of chromatin via recruitment of Polycomb complex so that messenger RNA could not be transcribed from them. Additional lncRNAs, currently defined as RNAs of more than 200 base pairs that do not appear to have coding potential, have been found associated with regulation of stem cell pluripotency and cell division.