Lecture 49 - 1 Dr. Joanna Long MBI LG-126...

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Unformatted text preview: 1 Dr. Joanna Long MBI LG-126 [email protected] Office hours: 2-4 pm on Thursdays or by appointment Lectures 49-54 (Lectures 47-48 after 54) Today’s lecture: Transcription (pp. 980-1020) Preprinted lecture notes 66-69, 98-104 Download (suggested) from http://biochem.med.ufl.edu/coursetemp.php?cid=44 or http://www.mbi.ufl.edu/facilities/msg/bch4024-notes.html Flow of genetic information --- the “Central Dogma” DNA RNA Protein Replication Transcription Translation messenger RNA (mRNA) transfer RNA (tRNA) ribosomal RNA (rRNA) 2 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 François Jacob and Jacques Monod noted mutants of E. coli which had errors in regulating the production of β- galactosidase and proposed a macromolecular repressor regulated the level of enzyme production ¾ They hypothesized the repressor binds to a specific operator sequence in DNA (1961) ¾ This is now known as the operon model Transient messenger RNA (only observed with more sensitive radiolabeling) Stable ribosomal RNA (seen by UV at A 260 ) has three characteristic molecular weights K. Asano, J. Mol. Biol . 14:71-84 (1965) Differentiating RNA 3 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: 3-4 minutes (allows rapid adaptation) Eukaryotes: hours-days ¾ Only one strand of DNA is transcribed for a particular gene—...
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This note was uploaded on 06/07/2011 for the course BCH 4024 taught by Professor Allison during the Fall '08 term at University of Florida.

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Lecture 49 - 1 Dr. Joanna Long MBI LG-126...

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