BCH4024 - Long Lecture 49 - 50

BCH4024 - Long Lecture 49 - 50 - Dr. Joanna Long MBI LG-126...

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1 Dr. Joanna Long MBI LG-126 (McKnight Brain Institute ground floor) jrlong@mbi.ufl.edu Office hours: 2-4 pm on Fridays or by appointment Lectures 52-57 Lecture notes at UF Elearning: http://lss.at.ufl.edu Today’s lecture: Transcription (Chapter 27) Download Quiz questions to prepare for exam FINAL EXAM 4/28 7:30-9:30 AM (Lectures 45-57; not cumulative) Syllabus for next 6 lectures 52) 4/14 Transcription (Chapter 26) 53) 4/15 Transcription processing (Chapter 26) 54) 4/16 Translation I (Chapter 27) 55) 4/18 Translation II and protein targeting (Chapter 27) 56) 4/21 Transcriptional regulation (Chapter 28) 57) 4/22 Eukaryotic transcriptional regulation (Chapter 28) Final exam 4/28 7:30-9:30 AM (Lectures 45-58) Notes posted at http://lss.at.ufl.edu
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2 Flow of genetic information --- the “Central Dogma” DNA RNA Protein Replication Transcription Translation messenger RNA (mRNA) transfer RNA (tRNA) ribosomal RNA (rRNA) RNA transcription is actively regulated ¾ Not all DNA is transcribed in a given cell (less than 50% even in prokaryotes) ¾ For example, E. coli only produces the enzymes needed for lactose utilization when lactose is in the growth media ¾ Making RNA and proteins takes energy Messenger RNA --- information link between DNA / ribosomes ¾ Heterogeneous in size like the proteins transcribed from mRNA ¾ Rate of synthesis: ~ 50 nucleotides/sec/molecule (DNA replication is up to 1000 nucleotides /sec/molecule) ¾ Fidelity: error rate of about 10 -5 (DNA is 10 -9 -10 -10 ) ¾ Degradation (t 1/2 ) is fast compared to other RNAs and DNA Prokaryotes: 1-4 minutes (allows rapid adaptation) Eukaryotes: hours-days ¾ Only one strand of DNA is transcribed for a particular gene—”sense strand” is not transcribed so mimics RNA ¾ Only a small fraction of the total DNA is transcribed
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3 RNA polymerization in contrast with DNA replication Similarities Uses ribonucleoside triphosphates Requires DNA template Chain growth 5’ Æ 3’ High fidelity (although not as high) Transcription A Æ U T Æ A C Æ G G Æ C Replication A Æ T T Æ A C Æ G G Æ C RNA DNA Differences No primer required for chain initiation Unwinds only a local region (~ 17 bp) of DNA RNA is displaced as DNA rewinds Copies only one strand of DNA Disengages from DNA template at specific termination sequences RNA Polymerase: control center for RNA transcription Transcribes DNA in a 5’ Æ 3’ direction Uses 5’-ribonucleoside triphosphates to synthesis mRNA Selects specific DNA strand and sequence for transcription Unwinds and rewinds the DNA duplex Prokaryotes have a single RNA polymerase Eukaryotes have three separate RNA polymerases
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4 RNA Polymerase: Multiprotein complex 180° α 2 ββ σω α 2 Æ Chain initiation, interacts with regulatory proteins β Æ Chain initiation and elongation β Æ DNA binding σ Æ Promoter recognition and binding; loosely bound; has many different forms ω Æ Unknown Most common scenario: One-dimensional search process (the
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BCH4024 - Long Lecture 49 - 50 - Dr. Joanna Long MBI LG-126...

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