Chapter 13-pt4

Chapter 13-pt4 - Chapter 13: 344 - 350 Euka ryotic mRNA...

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Chapter 13: 344 - 350 – Eukaryotic mRNA (Cont.) I. Self-Splicing Introns A. In Tetrahymena, excision of group I intron is protein-independent (RNA splices itself; seen in 28S rRNA) 1. not considered enzyme activity b/c RNA is not regenerated to original form at the end of the rxn B. Steps of 1. pre-rRNA cleaved at 5’ splice junction as G is added to 5’ end of intron (so intron-containing strand starts w/ GA) 2. intron cleaved at 3’ splice junction (after G) 3. 2 exons are spliced 4. excised intron circularizes to produce lariat intermediate, C. Actual Ribozymes produced in lab D. RNA Editing – posttranscriptional insertion/deletion of nucleotides or conversion of 1 base to another 1. discovered in trypanosomes (protozoa) a. seqs COIII for subunit III of cytochrome oxidases & mRNA transcript for different protozoans (Tb, Cf, Lt) i. mRNA seq highly similar among 3 organisms, but only ii. Tb: has U nucleotides in mRNA that weren’t in the gene
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Chapter 13-pt4 - Chapter 13: 344 - 350 Euka ryotic mRNA...

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