Forensics

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Forensics

  1. 1. The Application of Recombinant DNA Technology In Forensic Science Made by: Sara Hassan Semester 5 Biotechnology Presented to:Dr.Amber Shehzadi
  2. 2. Forensic Science The application of scientific knowledge and methodology to legal problems and criminal investigations is called forensic science. it includes problems like paternity issues, exoneration, criminal identification, high profile crimes bases on CSI and evidence collected. The applications of molecular biology, technologies and genetics which center largely on the ability of DNA analysis of the evidence recovered from the crime scene. In the popular media, these techniques are called genetic fingerprinting, though the more accurate term used today is DNA profiling.
  3. 3. Sources of Biological Evidence Material Reference Blood and blood stains Semen and semen stains Bones Teeth Hair with root Hair shaft Saliva (with nucleated cells) Urine Feces Debris from fingernails Muscle tissue Cigarette butts Postage stamps Envelope sealing flaps Dandruff Fingerprints Personal Items: Razor blade, chewing gum, wrist watch, ear wax, toothbrush Budowle 1995 Budowle 1995 Gill 1994 Alvarez 1996 Higuchi 1988 Wilson 1995 Sweet 1997 Benecke 1996 Hopwood 1996 Wiegand 1993 Hochmeister 1998a Hochmeister 1991 Hopkins 1994 Word 1997 Herber 1998 Van Oorschot 1997 Tahir 1996 ©2002 Academic Press
  4. 4. DNA Analysis DNA analysis consists of traditional and specializes techniques to distinguish between individuals of the same specie. Described by Dr. Alec Jeffrey in 1985. Traditional Techniques: Restriction fragment length polymorphism (RFLP), and short tandem repeat (STR) analysis.PCR analysis. Specialized Techniques: mitochondrial DNA (mtDNA) analysis, single nucleotide polymorphism, or SNP. http://ec.europa.eu/dgs/jrc/index.cfm?id=1410&obj_id=7360&dt_code=nws&lang=en
  5. 5. PCR of STR regions • PCR (polymerase chain reaction) analysis is usually the first step in the creation of a DNA profile today. • PCR replicates a small amount of DNA to create a larger sample for analysis. • It does this using a repeating process that takes about five minutes. First, a heat-stable DNA polymerase -- a special enzyme that binds to the DNA and allows it to replicate -- is added. Next, the DNA sample is heated it to 200 degrees F (93 degrees C) to separate the threads. Then the sample is cooled and reheated. Reheating doubles the number of copies. After this process is repeated about 30 times, there is enough DNA for further analysis.
  6. 6. PCR analysis 6
  7. 7. RFLP • Restriction Fragment Length Polymorphism we digest our DNA sample with restriction endonucleases • These fragments are separated by gel electrophoresis. • Blotting is done. • Probes are added • Corresponding image on Xray film is taken.
  8. 8. Short Tandem Repeats (STR) analysis • STR: repeated sequences of 3-5 base pairs (loci) which can be identified in a known data base. • Typically in non-coding intron region • Very useful in DNA analysis because they show great variability among individuals. • Does not require very much DNA, can be coupled with PCR. • (STR) technology evaluates specific regions (loci) that are found on DNA. • The variable (polymorphic) nature of STR regions intensifies the discrimination between one DNA profile and another. • Tested by gel electrophoresis or capillary electrophoresis 9
  9. 9. DNA Technology
  10. 10. CHANCES OF A MATCH … 12
  11. 11. Y-STR • • • • A Y-STR is a (STR) on the Y-chromosome. Y-STRs are used for paternity, and genealogical DNA testing. Y-STRs are taken specifically from the male Y chromosome. These Y-STRs provide a weaker analysis than autosomal STRs because the Y chromosome is only found in males, which are only passed down by the father, making the Y chromosome in any paternal line practically identical. • This causes a significantly smaller amount of distinction between Y-STR samples. Autosomal STRs provide a much stronger analytical power because of the random matching that occurs between pairs of chromosomes during the zygote making process
  12. 12. Mitochondrial Analysis • mtDNA technology analyzes DNA found in a different part of the cell, the mitochondrion • Old remains and evidence lacking nucleated cells — like hair shafts, bones, and teeth — that are unamenable to STR and RFLP testing yield results by mtDNA analysis. • all maternal relatives (for example, a person's mother or maternal grandmother) have identical mtDNA. • This enables unidentified remains to be analyzed and compared to the mtDNA profile of any maternal relative for the purpose of aiding missing persons or unidentified remains investigations.
  13. 13. Evidence tested: purified DNA PCR Amplification & sequencing mtDNA gel image Computer analysis and mtDNA profile comparisons. Mitochondrial DNA Analysis
  14. 14. DNA Technology • CODIS, which stands for Combined DNA Index System, is a program which consists of many databases that have DNA profiles useful for the criminal justice system • NDIS, or National DNA Index System, is the part of CODIS that contains DNA profiles at a national, state, and local level and is accessible to law enforcement all over the country
  15. 15. Related individuals have similar DNA profiles • • • • • Your DNA profile, like all other aspects of your genome, is inherited partly from your mother and partly from your father. Relationships within a family therefore become apparent when the alleles of a particular STR are marked on the family pedigree In this example, we see that 3 of the 4 children have inherited the 12-repeat allele from the father. This observation in itself is not sufficient to deduce that these three children are siblings, though the statistical chance would be quite high if the 12-repeat allele was uncommon in the population as a whole. Mt DNA from maternal side, Y STR for paternal side, STR alleles can be helpful for making a pedigree .
  16. 16. References • http://science.howstuffworks.com/life/genetic /dna-evidence3.htm • http://www.slideshare.net/DJPuNY/geneticsproject-7833335 • http://en.wikipedia.org/wiki/CSI_effect • http://www.slideshare.net/bleedingheart1200 9/dna-in-forensics-7047161?from_search=4

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