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The Gold Standard of DNA Extraction: Escaping the Cell

Explore the origins, technology, and ethical implications of DNA extraction, the foundation of forensic evidence. Learn the terminology and structure behind DNA, its extraction process, and its significance in identification procedures. Discover how DNA extraction revolutionized investigations and its role in modern forensic science.

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The Gold Standard of DNA Extraction: Escaping the Cell

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  1. DNA Extraction MakeupsTuesday – after school 2:20 sharp!

  2. The Gold Standard of Forensic Evidence: DNA By Sanford Herzon DNA Resource Center Montgomery County Public Schools Rockville, Maryland

  3. Escaping the cell • How it started • The technology • The chain reaction • The law • The ethical issues

  4. Escaping the cell • The Gold Standard • DNA Terminology • DNA Structure • DNA Extraction

  5. Federal Bureau of Investigation, 1997

  6. $5,000 for 200 rxns

  7. CSI: NIST

  8. “DNA has become the gold standard in the identification process” - Mike Coble when asked how DNA compares to other forensic evidence such as serology and fingerprints.

  9. Terminology • A chromosome is made of a DNA molecule. Humans have 46 chromosome in all body cells. • 46 chromosomes contains 3 billion codes (nitrogenous bases) of genetic information • A sequence refers a string of bases such as: ACTGCTC • A gene is a subunit of a chromosome. A gene codes for a specific trait like hair color or height.

  10. Terminology • Nuclear DNA – this refers to the 46 linear chromosomes found in the nucleus. Each parent contributes 23 chromosome to the offspring. • Mitochondrial DNA – one circular chromosome containing 37 genes. 13 of these genes are used in aerobic respiration to produce ATP (energy).

  11. Structure • Deoxyribonucleic acid • Molecule is referred to as “double helix” • Organic polymer made of repeating units called Nucleotides • 4. Nucleotides have 3 parts • 1. sugar – deoxyribose • 2. phosphate • 3. Nitrogenous bases • Adenine pairs with Thymine • Cytosine pairs with Guanine

  12. The Nucleotide

  13. DNA Extraction • Recipe for extracting DNA was discovered by Friedrich Meischer in 1869. • Today, most recipes involve four steps: • Centrifuge • Addition of lysis buffer • Addition of Salt solution • Addition of ethanol

  14. How WHS Agents Did it!

  15. Pellet the nuclei Ca++ Added Prep Buffer Added EDTA Mg++ Disorients phospholipids to breakdown nuclear membrane freeing the DNA Add SDS

  16. Add NaCl Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+

  17. Add EtOH

  18. Virtual Extraction Quiz– Due by Thursday, Dec. 19

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