4.27.10-RNA processing.bb - Exons are coding sequences or...

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Unformatted text preview: Exons are coding sequences or sequences that are represented in mature mRNA molecules. Introns are noncoding intervening sequences or interupting sequences that must be removed from the pre-mRNA before the mature mRNA is translated. Introns Electron microscopy of DNA:mRNA hybrid Exons Introns mRNA = Discovery of intervening sequences by R-looping Fig 26-12 The average human gene contains 8 introns The capping enzyme interacts with the CTD of RNA Pol II such that capping occurs before the complete synthesis of the RNA transcript. The organization of split Eukaryotic genes Fig 26-20 Note that the exons are much shorter than the introns Note also that the exon size is more conserved than the intron size The organization of the mammalian DHFR gene in three Representative species Mature mRNA is only ~6kb 1. 5 capping - 7 mGppp 2. splicing 3. 3 polyadenylation Processing of mRNA in Eukaryotes Not found in prokaryotes! Methylation of several specific sites located at the 5-end of eukaryotic pre-mRNAs is an essential step in mRNA maturation Methyl groups often are added at the 2 OH of the first and second nucleotides adjacent to the cap CAP The capping of eukaryotic pre-mRNA...
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4.27.10-RNA processing.bb - Exons are coding sequences or...

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