Recovering DNA

Created by: AAntonianannetti
Created on: 08-05-19 10:12

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Recovering DNA
- Identification of biological evidence
  - Locating biological material is necessary before appropriate collection
    - Presumptive Tests - test which can establish the possibility that a specific bodily tissue/fluid is present
    - Confirmatory Tests - tests which can identify a specific biological material
    - Appropriate collection
      - Prevent contamination
        PPE
    - Appropriate Packaging
      - Prevent contaminaion
        Swabs, brown paper bags, tubes, wet/dry, frozen/ambient
- Types of biological material from a crime scene
  - Semen
    - A thick fluid containing sperm and other secretions from the male reproductive system
    - The positive identification of semen can be extremely important in sexual abuse cases
    - Presumptive Tests
      - Alternative Light Source (ALS), Seminal Acid Phosphate Test (SAP)
    - Confirmatory Tests
      - Visualisation of sperm following staining, Lateral flow strips, mRNA analysis and PSA
  - Blood
    - Composed of red and white cells suspended in a liquid matrix called plasma.
    - Generally visible to the naked eye but may not be clear against dark surface and if cleaning has been attempted.
  - Salvia
    - The fluid released when the mouth waters that plays an important role in both mechanical and chemical digestion
    - Presumptive Tests
      - Alternative Light Source and the Starch Iodine Test
    - Confirmatory Test
      - Lateral Flow Strips and mRNA analysis
- Degradation of DNA Samples
  - Forensic samples usually show degradation
    - More cellular material is required to produce a DNA profile
      - Sometimes it is not possible to produce a DNA profile
  - In practice 15 or more cells are required to generate consistently good-quality DNA profiles from fresh material

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Recovering DNA

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