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DNA Fingerprinting

DNA Fingerprinting. Sotheavy Vann. What is DNA Fingerprinting?. “The generation of a set of distinct DNA fragments from a single DNA sample” Aka DNA profiling, forensic DNA analysis, DNA testing, genetic fingerprinting, and DNA typing Invented by Alec Jeffreys in 1985. Historic Cases.

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DNA Fingerprinting

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  1. DNA Fingerprinting Sotheavy Vann

  2. What is DNA Fingerprinting? • “The generation of a set of distinct DNA fragments from a single DNA sample” • Aka DNA profiling, forensic DNA analysis, DNA testing, genetic fingerprinting, and DNA typing • Invented by Alec Jeffreys in 1985

  3. Historic Cases • In 1988, the first criminal to be convicted based on supporting evidence of DNA fingerprinting was Colin Pitchfork. • In 1995, O. J. Simpson was acquitted based on sloppy DNA fingerprinting technique. • DNA fingerprinting was used to identify Abraham Lincoln with Marfan’s Syndrome.

  4. Common Uses • More often use to exclude suspects than to identify criminal (CODIS and NDIS) • Paternity test • Identifying genetic disorder • Ancestry analysis • Identifying a body

  5. Types of Samples • Blood • Hair • Saliva • Semen • Vaginal canal swab • Body tissue

  6. Types of DNA Fingerprinting Technique • RFLP analysis • VNTR analysis • PCR analysis • STR analysis • RAPD analysis • AFLP analysis • Mitochondrial analysis • Y-chromosome analysis

  7. Types of DNA Fingerprinting Technique 1. Restriction Fragment Length Polymorphism (RFLP) analysis • The sequence between between two restriction sites varies in length • Southern Blotting • Requires more DNA • More specific than PCR method • Time consuming • Need prior knowledge of genome

  8. Types of DNA Fingerprinting Technique 2. Variable number tandem repeats (VNTR) • PCR • 9-80 or more nucleotide sequence repeated as compared to RFLP which is 1-2 kilo base pairs • Both are reproducible

  9. Types of DNA Fingerprinting Technique 3. PCR analysis • DQA1 • For older samples • Determine presence or absence of certain alleles • Less DNA is needed • Less specific • Simple and fast

  10. Types of DNA Fingerprinting Technique 4. Short Tandem Repeats (STR) analysis • A type of VNTR • 2 to 6 nucleotides sequence repeated multiple time • PCR • Requires prior knowledge of genome to create primer

  11. Types of DNA Fingerprinting Technique 5. Random Amplified Polymorphic DNA (RAPD) analysis • Uses low-stringency PCR conditions • Prior genomic knowledge is not needed • Interpreting results can be challenging

  12. Types of DNA Fingerprinting Technique 6. Amplified Fragment Length Polymorphism (AmpFLP or AFLP) analysis • Detect absence or presence of polymorphism • Highly specific • Capable of amplifying 50 to 100 fragment simultaneously • Prior genomic knowledge is not needed • Highly reproducible

  13. Types of DNA Fingerprinting Technique 7. Y-chromosome analysis • Examines genetic markers in Y chromosomes (males only) • Used in sexual assault cases that involves more than one male suspects

  14. Types of DNA Fingerprinting Technique 8. Mitochondrial analysis • Use mtDNA, sample does not need to have nucleated cells • Old samples

  15. Step 1 of DNA Fingerprinting • Collect sample of DNA • Isolate DNA • Centrifuge • Detergent

  16. Step 2 of DNA Fingerprinting • Cut • Restriction enzymes • Sort • Gel electrophoresis or size fractionation

  17. Step 3 of DNA Fingerprinting • Denature DNA • Transfer DNA to nitrocellulose membrane

  18. Step 4 of DNA Fingerprinting • Add radioactive probe • Allow to hybridize

  19. Step 5 of DNA Fingerprinting • Autoradiography • Analyze DNA profile by comparison

  20. Southern Blot Virtual Lab • http://www.pbs.org/wgbh/nova/education/body/create-dna-fingerprint.html

  21. Problems • High probability for sample to be contaminated • Fake DNA evidence • Chimerism • Two different set of genes • VNTRs are not distributed evenly throughout racial population

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