SNPs

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  • SNPs - Single Nucleotide Polymorphisms
    • Pros
      • SNPs are able to withstand degraded DNA samples better than STRs in PCR
      • Sample processing and data analysis may be fully automated due to size-based separation not being needed.
    • A single based sequence variation between individuals at a particular point in the genome
      • Million of SNPs exist within the human genome
        • Can be used to identify individuals
          • Can be used in forensic cases
            • Several panels of SNPs have been developed that are designed to provide maximum discrimination powers
    • Cons
      • Mixtures of DNA - difficult to determine the difference
      • Inability to simultaneously  amplify enough SNPs from a small amount of DNA
    • SNP Detection
      • There are many techniques available for the resolutions of SNPs
        • In the 1970s, it was established that particular enzymes produced by bacteria could be used to cut the DNA molecule by recognising specific sequences
          • Restriction digestion can be used to genotype SNPs when the SNP either creates or destroys a particular restriction enzyme recognition sequence
            • Method is limited for forensic casework because it needs a large amount of DNA
    • SNP Databases
      • Efforts have been made to create a database of human variation of SNPs
    • Forensic Application
      • A vast amount of data is available on the different SNPs in the human genome, and one of the biggest tasks when applying SNPs to forensic applications is to select the most appropriate SNPs from the overwhelming numbers that are avilable
        • Dependant on the application
        • SNPs must be polymorphic
    • Forensic Identification
      • The vast majority of forensic DNA analysis involves the characterisation of biological material recovered from the scene of crime
        • Several panels of SNPs have been developed that are designed to provide maximum discrimination powers for forensic identification
          • These contain SNPs that are polymorphic
            • Forensic Value
              • Given the array of SNPs available in genome and with individuals differing at millions of positions
                • The potential for SNPs to discriminate between individuals is enormous
    • SNPs compared with STR loci

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