BIOL308 Lecture Notes - Rna Polymerase Ii, Rna Polymerase I, Gc-Content
16 Jul 2014
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Document Summary
Eukaryote pre-mrnas are subject to extensive post-transcriptional modification; processing. Only 0. 01% of genes in a typical eukaryotic cell are undergoing transcription at any given moment. Eukaryotic rnap does not recognize binding site by itself. Rna polymerase iv directs silencing of endogenous dna. Roles of rna polymerase iv in gene silencing. Control of gene expression similar to the mechanisms used in prokaryotic cells: Expression i soften controlled at the level of transcription initiations. Regulation by proteins that recognize specific regulatory sequences and modulate binding and activity of rnap. Early studies (1): rrna genes: rrna genes have high gc content (60% vs. 40%) rrna genes are repetitive (up to 20 000 copies of the gene/cell) rrna genes found in nucleolus. Early studies (2): rna synthesis under various conditions: High ionic concentration: rna with low gc content. Low ionic concentration: rna with high gc content (similar % to rrna) Mg2+ + low ionic strength: most of transcription in nucleolus.
