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Published byBruno Flowers Modified over 9 years ago
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Lecture 3 Introduction to recombinant DNA Technology
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Tools Enzymes Vectors Host DNA to be cloned
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Enzymes Nucleases Polymerases Ligases, Modifying enzymes
Topoisomerase,
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Exonucleases ExonucleaseI ssDNA 3-5 ExonucleaseIII dsDNA 3-5
Unit Enzyme 1ug DNA at 37C in 60 min in 50 ul reaction* ExonucleaseI ssDNA 3-5 ExonucleaseIII dsDNA 3-5 ExonucleaseVII ssDNA and 5-3
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How they cut Exo III
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Endonucleases Dnase I ssDNA, dsDNA
DNA template degradation in transcription reactions Removal of genomic DNA from RNA samples DNase I footprinting Nick Translation Mung bean nucleases ssDNA Removal of single-stranded extensions (3' and 5') to leave ligat able blunt ends Transcriptional mapping Cleavage of hairpin loops
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A Paternity Test
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Basic Structure of DNA to remember
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Iso schizomer Sph I (CGTAC^G) and Bbu I (CGTAC^G) Neo schizomer Sma I (CCC/GGG) and Xma I (C/CCGGG) Iso caudomer NheI G*CTAG C and AvrII C*CTAG G C GATC*G G GATC*C
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Neo schizomer
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Double digestion Double digestion is a process in which we use two restriction enzymes to cut so that molecules do not snap back on itself or for orientation certainty
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RIBONUCLEASES RNase A Bovine pancreatic RNase A, Rana pipiens RNaseH
RNase H family can be found in nearly all organisms, from archaea to bacteria and eukaryota. Rnase III Double stranded RNA degradation RNAi, microRNA
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Rnase based therapeutic for cancer
Onconase down regulates microRNA expression through targeting microRNA precursors Cell Research (2012) 22:1199–1202. doi: /cr ; published online 24 April 2012
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Rnase H of HIV and HBV as an example
1- Structural Basis for the Inhibition of RNase H Activity of HIV-1 Reverse Transcriptase by RNase H Active Site-Directed Inhibitors Journal of Virology
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Ligase
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Ligases and Ligastion T4 DNA ligase
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What Ligase needs to make an efficient ligation
5 Phosphate is absolute requirement If removed ligation can not take place Adjusting the vector insert ratio 1:3 formula? Contamination in DNA also influence ligation efficiency
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Need of Alkaline phosphatase (CIAP)
An enzyme that removes phosphatase from it substrate Why we need to remove the phosphate if it absolutely required How DNA is ligated after use of CIAP
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Need of Alkaline phosphatase (CIAP)
An enzyme that removes phosphatase from it substrate Why we need to remove the phosphate if it absolutely required How DNA is ligated after use of CIAP
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E.coli DNA polymerase I Nick translation
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Polymerase
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Klenow fragment Fill in reaction
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Bacteriophage T4 Polymerase
Active single-stranded 3'->5' exonuclease (ss DNA) (stronger than that of the Klenow fragment) Fill in Trimming back
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The T7 polymerase Enzyme has very high proof reading and polymerization The enzyme chemically or genetically modified High processivity, and fast polymerase rate Used in DNA sequencing
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Taq DNA polymerase Thermus aquaticus
PCR optimization, Pfu DNA polymerase Pyrococcus furiosus PCR (if DNA has to use in cloning)
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Terminal De-oxynuclotidyl Transferase Probe preparation tailing method
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AMV reverse transcriptase
HIV-1 reverse transcriptase from human immunodeficiency virus M-MLV reverse transcriptase from the Moloney murine leukemia virus AMV reverse transcriptase from the avian myeloblastosis virus
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RNA polymerases S6 RNA Polymerases T7RNA Polymerases
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Plasmid Isolation Solution 1 Solution 2 Solution 3 50 mM Tris pH 8
200 mM NaOH 3 M Potassium 10 mM EDTA 1 % SDS Acetate pH 5.5 Re suspends the pellet and maintains the pH and ability to inhibit DNases Breaks the cell wall to release the content. Denatures the DNA (Breaks H Bonds) At nutralization The Chromo DNA aggregates being very large while plasmid can not as it is cccDNA
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Alkaline de naturation and plasmid isolation
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Uses of different enzymes
Primer removal from PCR mixtures: Exo1 thermo prior to PCR product sequencing (see Reference 2) for one-tube "megaprimer" PCR mutagenesis (see Reference 3) Removal of single-stranded DNA containing a 3'-hydroxyl terminus from nucleic acid mixtures Assay for the presence of single-stranded DNA with a 3'-hydroxyl terminus (see Reference 4)
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