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Dna Technology


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Dna Technology

  1. 1. DNA TECHNOLOGY DNA Profiling & Identification
  2. 2. Use of DNA <ul><li>since 1987, DNA analysis has made appearances in US courtrooms </li></ul><ul><li>originally known as “DNA fingerprinting” it is now called DNA profiling or typing </li></ul><ul><li>used in less than one percent of all criminal cases </li></ul>
  3. 3. Use of DNA <ul><li>can quickly eliminate a suspect, saving time in searches for perpetrators </li></ul><ul><li>provides compelling evidence to support a conviction </li></ul><ul><li>reduces the chance of a wrongful conviction </li></ul>
  4. 4. Success of DNA in Courtroom <ul><li>depends on </li></ul><ul><ul><li>proper handling of evidence </li></ul></ul><ul><ul><li>careful unbiased analysis </li></ul></ul><ul><ul><li>fair & appropriate interpretation of results </li></ul></ul><ul><ul><li>accurate & effective reporting of results to judges and jurors </li></ul></ul>
  5. 5. Methods of DNA Analysis <ul><li>Restriction Fragment Length Polymorphism (RFLP) </li></ul><ul><li>Polymerase Chain Reaction (PCR) </li></ul><ul><li>Short Tandem Repeat (STR) </li></ul><ul><li>Mitochondrial DNA (mtDNA) </li></ul><ul><li>Y-Chromosome Analysis </li></ul>
  6. 6. RFLP - restriction <ul><li>analyzes the variable lengths of DNA fragments resulting from being cut with a restriction enzyme </li></ul><ul><li>enzyme cuts DNA at a specific sequence pattern known as a recognition site </li></ul><ul><li>presence or absence of recognition sites in a DNA sample generates DNA fragments of variable lengths </li></ul>
  7. 7. RFLP – gel electrophoresis <ul><li>restricted DNA placed in well of gel in an electrophoresis tank and current is applied </li></ul><ul><li>DNA is negatively charged and will travel to the positive side of the tank </li></ul><ul><li>large pieces travel slowly, small pieces travel quickly </li></ul>
  8. 8. RFLP – hybridization <ul><li>fragments are hybridized – DNA probes bind to complementary DNA sequences in the sample </li></ul><ul><li>probes are usually radioactive and will expose an x-ray film (autoradiography) </li></ul><ul><li>increasing # of probes decreases the chance of a coincidental match </li></ul>
  9. 9. RFLP - analysis <ul><li>probed fragments exposed on film create a profile that can be compared to known samples </li></ul><ul><li>any profiles that are being compared must be run on the same gel </li></ul>
  10. 10. RFLP – pros/cons <ul><li>1 st application of DNA analysis to forensics </li></ul><ul><li>gives a positive match </li></ul><ul><li>not used widely today due to need for a relatively large amount of DNA </li></ul><ul><li>samples degraded by the environment do not work well </li></ul>
  11. 11. PCR Analysis <ul><li>used to make millions of exact copies of DNA from a sample (amplification) </li></ul><ul><li>sample can be as small as a few skin cells </li></ul><ul><li>highly degraded samples can be analyzed </li></ul><ul><li>prevention of contamination extremely important </li></ul>
  12. 12. STR Analysis <ul><li>used to evaluate specific regions (called loci) within DNA </li></ul><ul><li>variability in short tandem repeat regions can be used to distinguish one DNA profile from another </li></ul>
  13. 13. STR Analysis <ul><li>FBI uses a standard set of 13 specific STR regions of CODIS </li></ul><ul><li>odds of two people having the same 13 loci DNA profile is about 1 in a billion </li></ul>
  14. 14. mtDNA Analysis <ul><li>used to examine DNA from samples that cannot be analyzed by RFLP or STR which require nuclear DNA </li></ul><ul><li>all mothers have the same mtDNA as their daughters b/c mitochondria of each new embryo comes from the mother’s egg cell </li></ul>
  15. 15. mtDNA Analysis <ul><li>older samples that lack nucleated cellular material (like bones, teeth, hair) can be analyzed via this method </li></ul><ul><li>comparing mtDNA profile of unidentified remains with profile of potential maternal relative can be important technique </li></ul>
  16. 16. Y-Chromosome Analysis <ul><li>Y chromosome passed directly from father to son </li></ul><ul><li>analysis of genetic markers on Y chromosome useful for </li></ul><ul><ul><li>tracing relationships among males </li></ul></ul><ul><ul><li>analyzing biological evidence involving multiple male contributors </li></ul></ul>