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Current time:0:00Total duration:4:40
AP.BIO:
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Video transcript

what is a non-coding RNA well a non-coding RNA or an NC RNA as it is abbreviated is a functional RNA molecule that actually skips this last step and is not translated into a protein in other words they just go directly from transcription into an RNA molecule and then go off to perform any number vital functions within the cell and there are many examples of non-coding RNAs including micro rna's ribosomal RNA transfer RNA the list goes on and on and as we go through each of these different types and examples of non-coding RNAs you'll start to see that there's sort of an emerging theme here and that is that most of these non-coding RNAs participate in either transcription or translation in one capacity or another so let's start off with micro RNAs micro RNAs or mi RNAs function and transcriptional and post transcriptional regulation of gene expression and they do this by base pairing with complementary sequences within mRNA or messenger RNA molecules and this usually results in gene silencing through translational repression or target degradation in essence the mRNA to which these micro rnas bind are prevented from being translated or they are sent on a pathway for degradation now the next set of non-coding rnas that we'll be talking about are all involved in translation the first of which is ribosomal RNA now ribosomes are the cellular machinery used to translate mRNA into proteins and it is made up of one type of RNA molecule ribosomal RNA transfer RNAs are an adaptor molecule that links the codons in an mRNA strand to the corresponding amino acids and so this is another type of non-coding RNA that you'll see in translation the third type is called snow RNA which stands for small nuclei or RNA and it's a class of small RNA molecules that guide covalent modifications of ribosomal RNA transfer RNA and small nuclear rnas primarily through methylation which is the addition of methyl groups or pseudo your dilation which is the addition of an isomer of the nucleoside uridine now another class of non-coding RNAs are the small nuclear rnas or snrnas not to be confused with the Sno RNA is the small nucleolar rnas that we just talked about now small nuclear rnas get their name from the fact that the average length of these RNA molecules is approximately 150 nucleotides and their primary function is in the processing of pre mRNA in the nucleus they also aid in the regulation of transcription factors or a particular RNA polymerase RNA polymerase ii as well as maintaining telomeres which are the regions of repetitive nucleotide sequences at the end of a chromatid which protects the end of the chromosome from deterioration during chromosomal replication now snrna can be associated with a set of specific proteins and form complexes that are called small nuclear ribonucleoproteins or snrnps or sometimes people just call them snaps and there is a special snip complex called the spliceosome made up of five small nuclear rnas over 150 proteins that is responsible for splicing or removing the introns contained in messenger RNA which is a major step in the post-transcriptional modification that takes place in the nucleus of eukaryotes and the way that the spliceosome does this is that it binds to specific sequences in the pre messenger RNA strand and performs two sequential transesterification reactions that splice at the end and then ligate the two exons to form a mature mRNA so now you know a little bit more of some examples of non-coding rnas and some of the functions that they perform within the cell
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