Forensics - DNA

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  • Created by: Ashlee
  • Created on: 30-04-15 17:55
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  • DNA
    • any cell in a nucleus
    • white blood cells/semen/saliva
    • large molecule and prone to degradation
    • enhancement techniques available
    • forensic profiling
      • short tandem repeats (STR's)
        • measures the exact number of repeating nucleotide units of a microsatellite
      • polymerase chain reaction (PCR)
        • amplify a single copy or a few copies of a piece of DNA across several orders of magnitude, generating thousands to millions of copies of a particular DNA sequence
      • junk DNA
        • DNA that doesn't code for anything/make protein
      • phenotype vs genotype
        • phenotype = physical appearance due to inheritance
          • the dominant alleles e.g. brown eyes
        • genotype = genetic makeup of the specific characteristic of a cell/individual
          • the dominant and recessive alleles that make up a characteristic e.g. BB is brown eyes, Bb is brown eyes and bb is blue eyes
      • presumptive testing
    • success rates
      • blood 93%; saliva 76%; semen 81%; hair with root 53%; tissue 50%; cellular material 26-30%
      • depends on quantity, quality and interpretation difficulties
    • profiling methodology
      • SGM+
        • second generation multiplex plus
        • analyses 10 short tandem repeat markers and gender indicators for 28 cycles
      • DNA SenCE
        • enhancement for small samples
        • cleans and concentrates
      • LCN
        • = low copy number
        • able to get data from small or degraded samples
        • 34 cycles
      • MtDNA
        • mitochondrial DNA - passed down from mother
      • YSTR's
        • short tandem repeat on the Y chromosome
        • when dealing with sexual assualts
          • the DNA of both man and female could mix
            • females have no Y chromosome
      • DNA17
        • improved discrimination, sensitivity and comparability
        • 32 DNA components and a gender identifier
    • cell free DNA
      • touch DNA
      • transferred nucleated cells
      • free running nucleic acids in sweat
      • sloughed skin cells


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