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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 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 • 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.
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
Types of Samples • Blood • Hair • Saliva • Semen • Vaginal canal swab • Body tissue
Types of DNA Fingerprinting Technique • RFLP analysis • VNTR analysis • PCR analysis • STR analysis • RAPD analysis • AFLP analysis • Mitochondrial analysis • Y-chromosome analysis
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
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
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
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
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
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
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
Types of DNA Fingerprinting Technique 8. Mitochondrial analysis • Use mtDNA, sample does not need to have nucleated cells • Old samples
Step 1 of DNA Fingerprinting • Collect sample of DNA • Isolate DNA • Centrifuge • Detergent
Step 2 of DNA Fingerprinting • Cut • Restriction enzymes • Sort • Gel electrophoresis or size fractionation
Step 3 of DNA Fingerprinting • Denature DNA • Transfer DNA to nitrocellulose membrane
Step 4 of DNA Fingerprinting • Add radioactive probe • Allow to hybridize
Step 5 of DNA Fingerprinting • Autoradiography • Analyze DNA profile by comparison
Southern Blot Virtual Lab • http://www.pbs.org/wgbh/nova/education/body/create-dna-fingerprint.html
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