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Forensic DNA Fingerprinting: Using Restriction Enzymes
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Stan Hitomi Coordinator – Math & Science Principal – Alamo School San Ramon Valley Unified School District Danville, CA Kirk Brown Lead Instructor, Edward Teller Education Center Science Chair, Tracy High School and Delta College, Tracy, CA Bio-Rad Curriculum and Training Specialists: Sherri Andrews, Ph.D. sherri_andrews@bio-rad.com Leigh Brown, M.A. leigh_brown@bio-rad.com Forensic DNA Fingerprinting Kit Instructors
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Why Teach DNA Fingerprinting? Real-world connections Tangible results Link to careers and industry Laboratory extensions Standards-based
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Forensic DNA Fingerprinting Kit Advantages Standards Based Aligns with AP Biology Lab 6 Use of real restriction enzymes and electrophoresis of real DNA fragments Lab can completed in two 45 minute sessions Sufficient materials for 8 student workstations
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DNA structure DNA restriction analysis (RFLP) Agarose gel electrophoresis Molecular weight determination Simulation of DNA Fingerprinting Plasmid mapping The Forensic DNA Fingerprinting Kit Can Help You Teach:
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DNA Fingerprinting Real World Applications Crime scene Human relatedness Paternity Animal relatedness Anthropology studies Disease-causing organisms Food identification Human remains Monitoring transplants
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Workshop Time Line Restriction digest of DNA samples Introduction to DNA Fingerprinting and RFLP analysis Electrophoresis on Agarose gels Analysis and interpretation of results
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DNA Fingerprinting Procedure Overview
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Laboratory Quick Guide
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DNA Fingerprinting Procedures Day One
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DNA Fingerprinting Procedures Day Two
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DNA Fingerprinting Procedures Day Three
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DNA is Tightly Packaged into Chromosomes Which Reside in the Nucleus
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Model of DNA DNA is Comprised of Four Base Pairs
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Deoxyribonucleic Acid (DNA)
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DNA Schematic O CH 2 O PO O O Base CH 2 O P O O O Base OH Sugar O Phosphate
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DNA Restriction Enzymes Evolved by bacteria to protect against viral DNA infection Endonucleases = cleave within DNA strands Over 3,000 known enzymes
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Enzyme Site Recognition Each enzyme digests (cuts) DNA at a specific sequence = restriction site Enzymes recognize 4- or 6- base pair, palindromic sequences (eg GAATTC) Palindrome Restriction site Fragment 1 Fragment 2
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5 vs 3 Prime Overhang Generates 5 prime overhang Enzyme cuts
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Common Restriction Enzymes EcoRI – Eschericha coli – 5 prime overhang Pstl – Providencia stuartii – 3 prime overhang
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The DNA Digestion Reaction Restriction Buffer provides optimal conditions NaCI provides the correct ionic strength Tris-HCI provides the proper pH Mg 2+ is an enzyme co-factor
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DNA Digestion Temperature Why incubate at 37°C? Body temperature is optimal for these and most other enzymes What happens if the temperature istoo hot or cool? Too hot = enzyme may be denatured (killed) Too cool = enzyme activity lowered, requiring longer digestion time
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Restriction Fragment Length Polymorphism RFLP Allele 1 Allele 2 GAATTC CTTAAG GAATTC CTTAAG CTGCAG GACGTC CGGCAG GCCGTC PstIEcoRI 123 3 Fragment 1+2 Different Base Pairs No restriction site + MA-1A-2 Electrophoresis of restriction fragments M: Marker A-1: Allele 1 Fragments A-2: Allele 2 Fragments
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Agarose Electrophoresis Loading Electrical current carries negatively- charged DNA through gel towards positive (red) electrode Power Supply Buffer Dyes Agarose gel
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Agarose Electrophoresis Running Agarose gel sieves DNA fragments according to size –Small fragments move farther than large fragments Power Supply Gel running
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Chemistry in action…. Or… Ask your friendly chemist… about electro- phoresis and electrolysis.
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Chemistry of electrophoresis and electrolysis Electric fields and electric currents
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SDS-PAGE, DNA electrophoresis and the need for a gel matrix (sieving medium) Without a viscous medium, all molecules move at ~ the same rate in electric field Gel structure retards larger solute particles DNA molecules, SDS- proteins have ~ equal charge/mass Electrophoresis occurs between the electrodes (field- driven).
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Electrolysis always occurs during electro- phoresis. Cathode produces H 2 at twice the rate that anode produces O 2 Current is carried by solute ions. Electrons aren’t soluble in H 2 O. Example: TAE buffer; tris supplies cations (+), acetate supplies anions (-). Electrolysis occurs at the electrodes.
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Analysis of Stained Gel Determine restriction fragment sizes Create standard curve using DNA marker Measure distance traveled by restriction fragments Determine size of DNA fragments Identify the related samples
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Analysis using Vernier’s Logger Pro software Adaptable to many forms of Gel AnalysisTake or Import Gel ImageSet OriginSet ScaleSet Standard LadderAdd Lanes Leaves more time for students to Explore
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Standard Curve and Analysis Easy to View Results include: Gel Image Standard Curve Data Table One convenient page with all the Results
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Molecular Weight Determination Size (bp)Distance (mm) 23,00011.0 9,40013.0 6,50015.0 4,40018.0 2,30023.0 2,00024.0 Fingerprinting Standard Curve: Semi-log
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DNA Fingerprinting Lab Extensions Independent studies Plasmid DNA isolation (mini-preps) Plasmid mapping using restriction enzymes Southern blot analysis Introductory labs to electrophoresis: Kool-Aid/FastBlast pH indicator in buffer
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Plasmid Map and Restriction Sites Laboratory Extensions BamHI: EcoRI: HindIII: EcoRI+Hind III: 1 linear fragment; 7367bp 2 fragments; 863bp / 6504bp 3 fragments; 721bp/2027bp/3469bp 5 fragments; 721bp/863bp/947bp/1659bp/2027bp BamHI 7367bp EcoRI 863bp 6504bp Hind III 721bp 2027bp 3469bp EcoRI+ HindIII 2027bp 1659bp 947bp 863bp 721bp
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Bio-Rad’s Electrophoresis Equipment Electrophoresis Cells Power Supplies Precast Agarose Gels PowerPac ™ MiniPowerPac ™ Basic PowerPac ™ HCPowerPac ™ Universal Mini-Sub ® Cell GTWide Mini-Sub Cell GT
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Vernier’s Analysis Equipment White Light Transilluminator BlueView Transilluminator White Digital Bioimaging System Blue Digital Bioimaging System BlueView Transilluminator White Light Transilluminator White Digital Imaging System Blue Digital Bioimaging System
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Webinars Enzyme Kinetics — A Biofuels Case Study Real-Time PCR — What You Need To Know and Why You Should Teach It! Proteins — Where DNA Takes on Form and Function From plants to sequence: a six week college biology lab course From singleplex to multiplex: making the most out of your realtime experiments explorer.bio-rad.com Support Webinars
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