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Forensic Analysis of DNA

Forensic Analysis of DNA. Chapter 9. DNA. Genetic Material Double stranded; two strands of nucleotides http:// www.youtube.com/watch?v =ZGHkHMoyC5I Nucleotides have phosphate group, deoxyribose sugar, and nitrogenous base (adenine, thymine, guanine, and cytosine)

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Forensic Analysis of DNA

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  1. Forensic Analysis of DNA Chapter 9

  2. DNA Genetic Material Double stranded; two strands of nucleotides http://www.youtube.com/watch?v=ZGHkHMoyC5I Nucleotides have phosphate group, deoxyribose sugar, and nitrogenous base (adenine, thymine, guanine, and cytosine) DNA is copied into new DNA through DNA replication in nucleus http://www.youtube.com/watch?v=teV62zrm2P0 DNA is transcribed into mRNA in nucleus; mRNA is converted to proteins through translation at the ribosome

  3. DNA Replication

  4. Transcription—DNA to mRNA

  5. Restriction Enzymes Cut DNA has specific recognition sequence Extracted from bacteria Gives fragments of different sizes http://www.youtube.com/watch?v=lPdQwdGgyfQ

  6. Restriction Enzymes

  7. Polymerase Chain Reaction Makes many copies of small collected DNA samples Done prior to other testing Uses DNA polymerase, 2 kinds of primers, free nucleotides, and thermal cycler Uses heating to denature and cooling for annealing Can get 2n DNA double helices where n is the number of heating and cooling cycles http://www.youtube.com/watch?v=v4L7rvmBXbY

  8. PCR

  9. Repetitive DNA When during DNA typing, want to use non-coding repetitive DNA; not coding DNA Much more variation in non-coding DNA Tandem repeats; non-coding repetitive DNA VNTR—variable number tandem repeats; often used for DNA typing STR—short tandem repeats; used most often for DNA typing RFLP—restriction fragment length polymorphism; cut with restriction enzymes to make many fragments

  10. VNTR

  11. STR

  12. STR

  13. RFLP

  14. Electrophoresis Load negative DNA at black side of chamber into gel (agarose or polyacrylamide) DNA moves to positive electrode Small fragments move farther through the gel Buffer is used as electrolyte to help send current through gel http://www.youtube.com/watch?v=0x2Lh5Rq8e0&feature=related

  15. Electrophoresis

  16. DNA Typing--Identification http://www.youtube.com/watch?v=RCI9YhstHK4&feature=fvw

  17. Crime Scene DNA Analysis

  18. DNA Typing—Paternity Testing

  19. Paternity Testing

  20. Paternity Testing

  21. Hybridization DNA from electrophoretic gel is transferred to nylon membrane or paper filter DNA can be heated to be denatured Radioactive or fluorescent probe are used to find specific DNA section

  22. Hybridization

  23. DNA Typing Amplify with PCR Use restriction enzymes to make RFLPs of STR or VNTR sequence of genome Separate fragments with electrophoresis Match bands with known samples to determine identity Can be used for crime scene matching, paternity testing, and identifying corpses or body parts

  24. CODIS STR data for first 13 STRs are put into CODIS If use at least 6 STRs, matching process is very precise; 1 in 2,000,000 probability; Using all 13 makes the probability of an incorrect match being 1 in 575-900 trillion

  25. CODIS STRs

  26. Capillary Electrophoresis Use glass capillary tube with gel wrapping and buffer reservoir STRs move through column and as pass through column peak appears on attached computer instrument Peak diagram is called an electropherogram

  27. STR used for gender identification Uses amelogenin gene whose length is different in X and Y chromosome STR electrophoresis shows two separate bands for presence of X and Y chromosome in males Shows one band for 2 X chromosomes in females

  28. Gender ID with STR

  29. mtDNA Found outside nucleus is mitochondria Easier to get and can be taken from any relative of the same maternal lineage Same in all relatives from same maternal line; so not as specific of a match Can be gotten when burning, age, or environmental degradation has damaged genomic DNA

  30. Mitochondrial DNA

  31. DNA sources for collection Any cells from skin, in blood, cheek cells from saliva, epithelial cells in hair follicles Sweat, semen, ear war, mucus can also be used to extract cells for DNA typing

  32. Collection of Biological Evidence Photograph, sketch, describe, and collect Collect from body fluids, tissues, trash, laundry, placed often touched (handles, light switches; places licked (envelopes, lipstick, cigarettes, partially eaten food for drink); places where body fluids might be (clothing, tissues, sheets, pillows, condoms)

  33. DNA Evidence Package each DNA stained item separately in paper bag or well-ventilated container; closed containers can lead to moisture and growth of DNA digesting bacteria Obtain reference DNA—buccal cells or blood Avoid contamination—wear gloves; never cross-contaminate DNA from one piece of evidence with another; use different instruments for every piece of evidence

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