BISC 330 Spring 2011 Lecture 12

BISC 330 Spring 2011 Lecture 12 - BISC 330L: Biochemistry...

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ISC 330L: Biochemistry BISC 330L: Biochemistry ring Semester 2011 Spring Semester 2011 USC Lecture 12: Monday, 07 February 2011 1. Chapter 4: Flow of Genetic Information NA Replication ¾ DNA Replication ¾ Transcription
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Three functions of DNA as the genetic material: 1. Storage of genetic material Contains the DNA 2. Contains the information that directs its own l i t i NA duplication RNA 3. Must contain the information that directs the assembly of proteins ROTEIN PROTEIN
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Fig. 4.16 Diagram of semi conservative DNA replication.
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Density Gradient Centrifugation: In terms of density, RNA > DNA > Protein > Lipid . A concentrated CsCl solution (density 1.7 gm/ml), containing cell extract, upon utlra centrifugation (100,000 x g), creates a density gradient (1.6 1.8 gm/ml) that gives very good separation of RNA and DNA from each other and from Lipids & Proteins. Lipids & Proteins float on top of the CsCl solution, while RNA and DNA form distinct bands in the solution, at the Levels equal to their densities.
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Fig. 4.14 Resolution of 14 N DNA and 15 N DNA in CsCl density gradient (Ultracentrifugation). ¾ To obtain 15 N DNA Meselson and Stahl grew DNA DNA E. coli for several generations in medium ntaining 15 H l as heavy light containing NH 4 Cl as sole nitrogen source. hen they introduced ¾ Then they introduced 14 NH 4 Cl as nitrogen source.
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Detection of semiconservative DNA replication in E. coli , by Meselson & ahl Stahl, 1958.
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Importance of 14 N/ 15 N and Centrifugation * * *
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DNA Replication Basics ¾ Catalyzed by DNA polymerases (there are three DNA pol I, II, and III) none of these alone can initiate DNA chains, in either direction ¾ Direction of synthesis is 5’ Î 3’ iti ti i “i ith f 3’OH ¾ Initiation requires a “primer” with a free 3’OH ¾ 3’OH attacks phosphate on incoming nucleoside triphosphate ¾ Both strands of DNA are duplicated at the same time ¾ DNA polymerase cannot unwind duplex by itself any cessory proteins are required ¾ Many accessory proteins are required
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Replication of a circular bacterial DNA from one origin karyotic replication Eukaryotic replication
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¾ DNA polymerase replicates DNA by using dNTPs to extend
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This note was uploaded on 02/15/2012 for the course BISC 330L taught by Professor Petruska,tower during the Spring '07 term at USC.

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BISC 330 Spring 2011 Lecture 12 - BISC 330L: Biochemistry...

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