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Wednesday 4/9/14

Wednesday 4/9/14. AIM: How is DNA useful to forensic science? DO NOW: List at least 4 sources of DNA that could be extracted from a crime scene HOMEWORK: Text read pages 343-348. questions 9-11 pages364-365. DNA: deoxyribonucleic acid. It is a polymer

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Wednesday 4/9/14

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  1. Wednesday 4/9/14 • AIM: How is DNA useful to forensic science? • DO NOW: List at least 4 sources of DNA that could be extracted from a crime scene • HOMEWORK: Text read pages 343-348. questions 9-11 pages364-365

  2. DNA: deoxyribonucleic acid • It is a polymer • Big molecule made of repeating subunits • DNA is a chain of Nucleotides • a nucleotides is made of three parts: a phosphate, a nitrogenous base, and a 5 carbon sugar.

  3. Forensic source of DNA • Blood and bodily fluids are the most common sources • Which part of blood gives us DNA? • Leokocytes: White blood cells • A single drop of blood may contain 7,000 to 25,000 white blood cells • DNA fingerprint or profile

  4. DNA fingerprint • Identify the potential suspect • Clear wrongfully suspected person • Identify crime and victims • Establish paternity and family relationships • Match organ donors

  5. Wednesday 4/9/14 • AIM: How is DNA manipulated in the Forensics lab? • DONOW: Explain how you would separate a blood sample to extract DNA • HW: Page 364 q 1-3 • Last night was 9-11

  6. Preparing DNA for analysis • Isolate or remove DNA from sample ex: skin, clothing, weapon • Extract DNA from the cells (centrifuge) • Enzymes are then used to isolate DNA from chromosome • Enzyme: protein catalyst: causes a chemical reaction that may not ordinarily take place

  7. DNA profiling, testing, typing or genetic fingerprint • Process that identifies individuals based on their individual DNA

  8. DNA Fingerprinting Real WorldApplications • Crime scene • Human relatedness • Paternity • Animal relatedness • Anthropology studies • Disease-causing organisms • Food identification • Human remains • Monitoring transplants

  9. Collect Buccal Cells

  10. Steps to making a DNA fingerprint • 1- Extract DNA from cell nucleus • 2- Add restriction enzymes to cut DNA into pieces • 3- Separate fragments with gel electrophoresis • 4- Make a copy of results using southern blot • 5- add radioactive DNA probe to visualize • 6- visualize fragments and analyze results

  11. Forensic DNA Fingerprinting: Using Restriction Enzymes

  12. DNA Fingerprinting ProceduresDay One

  13. DNA DigestionTemperature Why incubate at 37°C? • Body temperature is optimal for these and most other enzymes What happens if the temperature is too hot or cool? • Too hot = enzyme may be denatured (killed) • Too cool = enzyme activity lowered, requiring longer digestion time

  14. DNA Fingerprinting ProceduresDay Two

  15. DNA Fingerprinting ProceduresDay Three

  16. Electrophoresis Analysisof Stained Gel Determine restriction fragment sizes • DNA marker • Measure distance traveled by restriction fragments • Determine size of DNA fragments Identify the related samples

  17. Thursday 4/9/14 • AIM: how are DNA fragments separated? • DO NOW: What is the function of a restriction enzyme? • 2 minute mystery Big dipper • Homework: Textbook page 365 q 17

  18. Why would you use restriction enzymes in a forensics lab? To cut up DNA samples and create a DNA fingerprint to identify a piece of evidence

  19. Would you make an arrest based on the evidence below?

  20. Restriction Fragment Length Polymorphism • R:Restriction: enzymes are used to cut the DNA • F-fragments: creates many pieces of DNA • L-length of each fragment varies among individuals • P-polymorphisms: greek term meaning many shapes

  21. Restriction Endonucleases Also called restriction enzymes Cleave or cut DNA 1962: “molecular scissors” discovered in in bacteria E. coli bacteria have an enzymatic immune system that recognizes and destroys foreign DNA 3,000 enzymes have been identified, around 200 have unique properties, many are purified and available commercially

  22. Pd 3 Friday 4/11/14 • AIM: how can we separate DNA fragments? • DO NOW: how were restriction enzymes first found?

  23. “Able was I, ere, I saw Elba” 5’-GGATCC-3’ 3’-CCTAGG-5’ Bam H1 site: Restriction Endonucleases Recognition sites have symmetry (palindromic)

  24. Restriction Enzymes Pt 1 - YouTube

  25. Enzyme Site Recognition Restriction site Palindrome • Each enzyme digests (cuts) DNA at a specific sequence = restriction site • Enzymes recognize 4- or 6- base pair, palindromic sequences (eg GAATTC) Fragment 2 Fragment 1

  26. 5 vs 3 Prime Overhang Enzyme cuts • Generates 5 prime overhang

  27. Common Restriction Enzymes EcoRI – Eschericha coli – 5 prime overhang Pstl – Providencia stuartii – 3 prime overhang

  28. Restriction enzymes

  29. Restriction Endonucleases Restriction enzyme animation http://www.dnai.org/b/index.html

  30. NOW WHAT … Separate the fragments

  31. Gel electrophoresis • The standard method for separating DNA fragments is electrophoresis through agarose gels.

  32. Terms • Agarose is a polysaccharide (carbohydrate) polymer material, generally extracted from seaweed. • Gel electrophoresis is a method that uses an electrical current and a gel matrix to separate molecules like DNA and proteins. • Buffer a solution containing either a weak acid and its salt or a weak base and its salt, which is resistant to changes in pH.

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