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DNA Forensics

DNA Forensics. DNA Fingerprinting - What is It?. Use of molecular genetic methods that determine the exact genotype of a DNA sample in a such a way that the results distinguish one biological organism from another This unique genotype = DNA Profile. It ’ s not that complicated.

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DNA Forensics

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  1. DNA Forensics

  2. DNA Fingerprinting - What is It? • Use of molecular genetic methods that determine the exact genotype of a DNA sample in a such a way that the results distinguish one biological organism from another • This unique genotype = DNA Profile

  3. It’s not that complicated • A DNA fingerprint is a method of looking at the similarities and differences that exist in organisms’ DNA sequences • Distinguish one biological organism from another • Individually discriminating southern blot minisatellite hybridization profile

  4. How to do DNA FingerprintingThe Big Picture Collect Tissue Sample >20 cells >1000 cells RFLP / Southern blot RFLP / Southern blot PCR Analysis

  5. DNA Fingerprinting RFLP Determination of an individual’s unique collection of DNA restriction fragments

  6. How to do DNA FingerprintingThe Big Picture Collect Tissue Sample >1000 cells >20 cells RFLP / Southern blot RFLP / Southern blot PCR Analysis

  7. The majority of our genome is made up non coding DNA How much? Of this a large portion is of short sequences that are repeated, sometimes hundreds of times. There are numerous forms of this "repetitive DNA" Non Coding vs Coding DNA

  8. Short Tandem Repeats(STR’s) STR – region of DNA containing tandem copies of di-, tri- or tetranucleotide repeat units. Examples: Dinucleotide repeats: GTGTGTGTGTGT…… Trinucleotide repeats: ACGACGACGACG…… Tetranucleotide repeats: TATCTATCTATC……

  9. More on STRs • Number of repeats varies greatly between individuals • STRs make up 10-15% of the mammalian genome • STRs are also called “microsatellites”

  10. Possible Patterns for a Single “Gene” With Three Alleles In a standard DNA fingerprint, about a dozen sites are analyzed, with each site having many possible alleles.

  11. PCR = Polymerase Chain Reaction

  12. What is It? • Basically DNA replication in a tube • Needs the same basic components as DNA replication: • DNA nucleotides, the building blocks for the new DNA • Template DNA, the DNA sequence that you want to amplify • Primers, single-stranded DNAs between 20 and 50 nucleotides long that are complementary to a short region on either side of the template DNA • Taq polymerase, a heat stable enzyme that drives, or catalyzes, the synthesis of new DNA • Targets a particular sequence and amplifies it many many, many, many times

  13. PCRhttps://www.youtube.com/watch?v=2KoLnIwoZKU

  14. CODIS Loci • Combined DNA Index System • 13 Loci across human genome

  15. Multilocus analysis - 7 loci

  16. DNA Allele Interpretation • http://www.newscientist.com/article/mg20727733.500-fallible-dna-evidence-can-mean-prison-or-freedom.html#.U0f7lsYh5W4

  17. Grim Sleeper

  18. Monozygotic (Identical) and Dizygotic (Fraternal) twins STR Analysis MZ DZ DZ

  19. Mitochondrial DNA

  20. Y Chromosomal Inheritance

  21. https://genographic.nationalgeographic.com

  22. Homework • See Blackboard for Assignments for this Special Topic

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