Forensic DNA

1. Forensic DNA

2. Think Pair Share What is Dna?What does it do? What kind of forensic cases involve dna?

3. What does DNA do? DNA is the instruction manual for your cells

4. What is DNA? Target Region for PCR Deoxyribonucleic Acid chromosome cell nucleus Double stranded DNA molecule Individual nucleotides www.cstl.nist.gov/biotech/strbase/ppt/4

6. What makes up DNA? Double Helix • The sides or backbone of the DNA molecule are made up of sugar (deoxyribose) and phosphate molecules. • The rungs that form the middle of the molecule are made up of pairs of nucleotides or nitrogen bases. Adenine (A) pairs with thymine (T), while guanine (G) always pairs with cytosine (C). • The order of the bases determines the genetic code. DNA Image: http://science.howstuffworks.com/genetic-science/dna-evidence.htm

7. Label the diagram

8. DNA stands for deoxyribonucleic acid and contains genetic information. Itis found on chromosomes located in the nucleus of our cells.

9. Genetic Variation DNA is a unique, identifying type of evidence No two people have the same DNA, except _________ ? Inventory your inherited traits and see if anyone in the class has exactly the same Inventory

10. A Homologous Chromosome Pair • One from mom • One from dad • What is the difference? Image: greghampikian@bosiestate.edu

11. A Karyotype

12. Where is DNA found?

13. people constantly shed DNA

14. Sources of Biological Evidence • Blood • Semen • Saliva • Teeth • Bone • Tissue www.cstl.nist.gov/biotech/strbase/ppt/4

16. Imagine you are at a crime scene and are collecting evidence. Which of the following evidence are you collecting that could potentially contain DNA.

17. Hair Used tissue Fibers Eyeglasses Baseball hat A urine specimen Cigarette butt fingerprints

18. True or False? Which three statements below are true? 1. The DNA in a man's blood is the same as the DNA in his skin cells and saliva. 2. Every person on earth has different DNA. 3. DNA can be found in all the cells in our bodies except the skin cells. 4. DNA can have forensic value even if it is decades old. 5. DNA evidence was first used to get a conviction in a trial in 1987. Watch the video segment from NOVA: "The Killer's Trail" and be ready to answer the questions on the next slide.

19. Video Quiz • Choose the best answer for each. • 1. Who was the victim? • A. Marilyn Sheppard B. Sam Sheppard C. Sam Sheppard, Jr. • 2. What are the keys to DNA fingerprinting? • Chromosomes B. Alleles C. Nitrogen bases • 3. Where did the scientist get the sample of DNA for Marilyn Sheppard? • A. Hair B. Skin C. Fingernail • 4. Whose blood was found in the blood trail? • A. Marilyn Sheppard B. Sam Sheppard C. Neither

20. Why is DNA so important in forensic ? Can you list types of cases DNA can be used in?

21. NY State Police Forensic Investigation Center Biological Science Section

22. NYSP Forensic Biology

23. How is DNA used as evidence? • Each person’s DNA is different from other people (except identical twins). • DNA collected from a crime scene can either link a suspect to the evidence or eliminate a suspect, similar to the use of fingerprints. • DNA can identify a victim through DNA from relatives, even when no body can be found. • DNA can link crime scenes together by linking the same perpetrator to different scenes locally, statewide, and across the nation. • DNA can place an individual at a crime scene, in a home, or in a room where the suspect claimed not to have been. DNA Strand Image & information : http://www.dna.gov/audiences/investigators/know/

24. Human Identity Testing • Forensic cases -- matching suspect with evidence • Paternity testing -- identifying father • Historical investigations • Missing persons investigations • Mass disasters -- putting pieces back together • Military DNA “dog tag” • Convicted felon DNA databases

25. Think: Pair: Share Whose DNA should go in the Database What happens to the DNA that is put in a database (who has access to this database? )

26. DNA is convicting the guilty and freeing the innocentClarence Harrison, 2004 Local DNA expert helps overturn Georgia conviction08:56 AM PDT on Wednesday, September 1, 2004 Adam Atchison / KTVB…Thanks in part to the efforts of Hampikian and his team, Georgia resident Clarence Harrison walked out of the courtroom a free man on Tuesday. Just last week, Hampikian reviewed new DNA test results and discovered Harrison’s DNA doesn't match the evidence saved from the scene of a rape and robbery in 1986 …

27. Others freed by DNA evidence Images by: greghampikian@bosiestate.edu

28. DNA Use in Forensic Cases • Most are rape cases (>2 out of 3) • Looking for match between evidence and suspect Challenges • Mixtures must be resolved • DNA can be degraded (bacteria, fungi, sunlight, heat) • Inhibitors to PCR can be present (heme, dyes…) Modified from www.bioforensics.com

29. What factors affect DNA evidence? Several factors can affect the DNA left at a crime scene, such as environmental factors (e.g., heat, sunlight, moisture, bacteria, and mold). DNA information : http://www.dna.gov/audiences/investigators/know/

30. Collecting Packing and preserving DNA • Dry • Cold

31. Therefore, not all DNA evidence will result in a usable DNA profile. Further, DNA testing cannot identify when the suspect was at the crime scene or for how long.

34. PCR Amplification • DNA regions flanked by primers are amplified

35. 5’ 3’ 5’ 3’ Starting DNA Template 3’ 5’ 3’ 5’ Separate strands (denature) Forward primer 5’ 3’ 3’ 5’ 5’ 3’ 5’ 3’ Make copies (extend primers) Reverse primer Add primers (anneal) DNA Amplification with the Polymerase Chain Reaction (PCR) http://www.dnalc.org/resources/3d/19-polymerase-chain-reaction.html www.cstl.nist.gov/biotech/strbase/ppt/4

36. PCR (polymerase chain reaction) • The DNA doesn’t have to be recently collected, either; the PCR test can still be performed even years after--decades after--the fact, and still be just as accurate. • This is because the PCR method involves copying the available DNA

37. We only care about 13-16 areas • Of the 3,000,000,000 DNA bases, about 0.3% is not conserved: 1 million bases • Forensic STR analysis looks at the length of 13-16 areas of DNA

38. AATG Short Tandem Repeats (STRs) 7 repeats 8 repeats the repeat region is variable between samples while the flanking regions where PCR primers bind are constant www.cstl.nist.gov/biotech/strbase/ppt/4

39. 13 CODIS Core STR Loci TPOX D3S1358 TH01 D8S1179 D5S818 VWA FGA D7S820 CSF1PO AMEL D13S317 AMEL D16S539 D18S51 D21S11 www.cstl.nist.gov/biotech/strbase/ppt/4

40. What Do STR Profiling Results look Like? D3S1358 vWA FGA Amelogenin D18S51 D21S11 D8S1179 D5S818 D13S317 D7S820

41. x x 1 in 111 1 in 20 1 in 22,200 x x 1 in 100 1 in 14 1 in 81 1 in 113,400 x x 1 in 116 1 in 17 1 in 16 1 in 31,552 Statistical estimates: the product rule 1 in 10 = 0.1 1 in 79,531,528,960,000,000 www.bioforensics.com 1 in 80 quadrillion

42. Gel Electrophoresis http://learn.genetics.utah.edu/content/labs/gel/

43. DNA Probes

44. codis Combined DNA Index System

46. FBI’s CODIS DNA Database Combined DNA Index System • Used for linking serial crimes and unsolved cases with repeat offenders • Launched October 1998 • Links all 50 states • Current backlog of >600,000 samples

47. The Combined DNA Index System (CoDIS) • A database of DNA profiles from violent felons and crime scene samples • Laws concerning who is eligible for the database vary from state to state

48. CSI Reality Check

49. The Mystical Power of CoDIS • Extremely powerful investigative tool, linking crimes, and pulling suspects out of thin air! • Can prevent, as well as solve crimes!

50. How good is DNA at exonerating? • Crime labs report about 25% of samples sent by law enforcement do not match primary suspect • (FBI, GBI, Virginia, Connecticut, Justice Department)