Lecture 11

Lecture 11 - LS3 MOLECULAR BIOLOGY LECTURES 11-20 Spring,...

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LS3 MOLECULAR BIOLOGY LECTURES 11-20  Spring, 2008 Dr. Randolph Wall Boyer Hall (MBI) 539A Final Exam Tue, June 10, 6:30-9:30P
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LS3 MOLECULAR BIOLOGY Spring, 2007, Second Half Lectures/Dates Topics 11 May 6 12 May 8 Translation I: 13 May 13 Translation II: Ribosomes & Protein Synthesis 14 May 15 15 May 20 16 May 22 17 May 27 18 May 29 Analyzing Cloned Genes, Gene Chips 19 June 3 Genomes, RNA Regulation of Genes 20 June 5 Final Exam Review June 10 Final Exam
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LS3 MOLECULAR BIOLOGY LECTURE 11  May 6, 2008 Eukaryotic Genes and mRNA  Processing Dr. Randolph Wall Reading:  Watson et al., 371-374, 379-387, 391-395, 398-403, 406-409
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Eukaryotic Gene Structure and Expression is More Complex  than in Prokaryotes  Prokaryotes mRNA is exact replica of gene Transcription and translation occur in the same compartment Transcription and translation of mRNA are coupled Eukaryotes mRNA is not replica of gene Transcription takes place in nucleus, Translation in cytoplasm Nuclear mRNA precursors (pre-mRNA) undergo RNA  processing(capping, splicing, polyA addition) -> mRNAs  that are  transported to cytoplasm for translation Transcription & mRNA processing events are coupled
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From Lodish et al (2004) Molecular Cell Biology.  W.H. Freeman & Co.
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RNAs in Eukaryotes are made from larger precursors by RNA  processing Types and amounts of RNA in eukaryotic cells cytoplasmic RNAs: ribosomal RNA (rRNA)  80% of total transfer RNA (tRNA)  15% of total messengerRNA (mRNA) ~3% of total nuclear RNAs: precursor RNAs, small RNAs ~2% of total All types of RNA in higher eukaryotic cells are processed from larger  precursors RNA processing directed by specific sequences in precursor RNAs
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Discovery of mRNA Processing Early experiments indicated that mRNA was synthesized as a longer  precursor in the nucleus This larger class of nuclear RNAs referred to as heterogenous nuclear  RNA (hnRNA) has many different sizes (from 5,000 - 50,000 nt  long)  mRNA associated with cytoplasmic polyribosomes was smaller than  hnRNA (mostly <5000 nt long) Breakthrough Discoveries: mRNA and hnRNA found to contain 5’  RNA precursors  (now called pre-mRNA) - discovered in early 1970s  by several labs: J. Darnell  (3’ polyA) A. Shatkin, R. Perry (5’ caps)
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    Pulse/chase expt: Pulse/chase expt:           hnRNA -> mRNA hnRNA -> mRNA       1. 30 min pulse label
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Lecture 11 - LS3 MOLECULAR BIOLOGY LECTURES 11-20 Spring,...

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