Post Transcriptional Modifications || mRNA processing || 5' Capping || Poly A Tail || Splicing скачать в хорошем качестве

Post Transcriptional Modifications || mRNA processing || 5' Capping || Poly A Tail || Splicing

#PostTranscriptionalModifications #mRNA #ProteinSynthesis Hello and welcome to this video on post-transcriptional modifications. In this video, we will learn about how mRNA is processed in prokaryotes and eukaryotes before it can be translated into a protein. mRNA is a type of RNA that carries the genetic information for making proteins. It has three main parts: a 5' untranslated region (5' UTR) at the beginning, a protein-coding region in the middle, and a 3' untranslated region (3' UTR) at the end. In prokaryotes, the mRNA is ready for translation as soon as it is transcribed from DNA. There is no need for any further modifications. Prokaryotes do not have a nucleus, so the mRNA can be translated by the ribosomes in the cytoplasm while it is still being transcribed by the RNA polymerase. This means that transcription and translation happen at the same time in prokaryotes. In eukaryotes, there is a nucleus, so transcription and translation are separated. The initial RNA transcript is called pre-mRNA, which needs to be processed in the nucleus before it becomes mature mRNA. The first step in processing the pre-mRNA in eukaryotes is adding a 5' cap. This is a modified guanine nucleotide that is attached to the 5' end of the transcript with a special 5'-to-5' bond. Then, some methyl groups are added to the cap and the next two nucleotides. The cap helps the ribosome to recognize and bind to the mRNA in the cytoplasm. The last step in processing the pre-mRNA in eukaryotes is adding a 3' poly(A) tail. This is a string of adenine nucleotides that is added to the 3' end of the transcript. There is no specific sequence that signals the end of the gene, and sometimes the RNA polymerase may transcribe beyond the gene. There is a sequence, AAUAAA, in the pre-mRNA that marks the end of the 3' UTR. Some proteins recognize this sequence and cut the pre-mRNA 10-30 nucleotides after it. Then, another enzyme, poly(A) polymerase, adds the poly(A) tail to the cut 3' end. The poly(A) tail makes the mRNA more stable and protects it from being degraded by enzymes in the cytoplasm. The pre-mRNA transcript also contains non-coding sequences called introns, which are interspersed with the coding sequences called exons. The introns need to be removed from the pre-mRNA. This is called splicing. Splicing is done by complexes of small nuclear RNAs (snRNAs) and proteins called snRNPs (snurps). The snurps bind to the intron, cut its left end from the upstream exon, loop the intron back, cut its right end from the downstream exon, and join the two exons together. The result is mature mRNA without introns. After the pre-mRNA is processed, the mature mRNA leaves the nucleus and enters the cytoplasm. There, it is recognized by the ribosomes, which start to translate it into a protein. We hope you enjoyed this video and learned something new. If you did, please give it a thumbs up and subscribe to our channel for more videos on biology topics. Thank you for watching and see you next time.