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Forensic Sciences: DNA testing

Forensic Sciences: DNA testing. Forensic Sciences. The application of a broad spectrum of sciences to answer questions of interest to the legal system. Fields of Study. Latent Print analysis Toxicology Crime Scene Photography Document analysis Blood Spatter analysis Ballistics.

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Forensic Sciences: DNA testing

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  1. Forensic Sciences: DNA testing

  2. Forensic Sciences • The application of a broad spectrum of sciences to answer questions of interest to the legal system.

  3. Fields of Study • Latent Print analysis • Toxicology • Crime Scene Photography • Document analysis • Blood Spatter analysis • Ballistics • Fiber analysis • Arson • Explosives • DNA • Computer • Other

  4. Latent Print Analysis • Fingerprints • Palm prints • Footwear and tire impressions • Other – ears, lips, etc.

  5. DNA

  6. Are you just a number?

  7. Methods of identification

  8. What are some of the DNA technologies used in forensic investigations? • Restriction Fragment Length Polymorphism (RFLP) • PCR Analysis • STR Analysis • Mitochondrial DNA Analysis • Y-Chromosome Analysis

  9. Repetitive DNA in the Human Genome • Less than 2% codes for Proteins • 50% of the genome contains repeated sequences • No apparent function • Recombination? • Formation of new genes?

  10. Restriction Fragment Length Polymorphism (RFLP) http://www.youtube.com/watch?v=CfZkn7D6dro Interactive student in-silico activity http://www.pbs.org/wgbh/nova/teachers/body/create-dna-fingerprint.html

  11. What are STRs? • Short Tandem Repeats (STR) are repetitive sequences: • Tetranucleotide: AAAG AAAG AAAG AAAG • Trinucleotide: CTT CTT CTT CTT CTT • Dinucleotide: AG AG AG AG AG AG • Tetranucleotides are favored in human identity • Good balance of “ease of interpretation” and “variability found in nature”

  12. Original DNA target region Thermal cycle Thermal cycle Thermal cycle Exponential Amplification with PCR In 32 cycles at 100% efficiency, 1.07 billion copies of amplicon are made. http://www.cstl.nist.gov/div831/strbase/

  13. Allelic Ladder

  14. 1 in 18 1 in 20 1 in 50 1 in 44 2 loci: 1 in 360 3 loci: 1 in 18000 X X X 4 loci: 1 in 792000 9 loci: ~1 in 1010 16 loci: ~1 in 1017 Current World Pop: ~6.3 billion Discrimination power through multiplexing Allele possibilities Hypothetical likelihood of occurrence 1 locus: 1 in 18 Sample Genotype

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

  16. Sources of Biological Evidence • Blood • Semen • Saliva • Urine • Hair • Teeth • Bone • Tissue

  17. References and resources • http://www.cstl.nist.gov/biotech/strbase/intro.htm (some information in this presentation is from this ppt) • http://www.promega.com/applications/hmnid/ (Promega Human identity testing products) • http://www.promega.com/profiles/ (Profiles in DNA) • http://journalsip.astm.org/JOURNALS/FORENSIC/jofs_home.html (Journal of Forensic Science) • http://appliedbiosystems.com Supplier of Human identification systems

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