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Topic 6 (DNA Profiling (PCR (Cycle starts again with all 4 strands (2…

- - - - (each cycle doubles amount of DNA)
- - - - rigor mortis
        
        lactic acid builds up
        
        pH falls
        
        enzymes producing ATP are inhibited
        
        anaerobic respiration
        
        muscles are deprived of oxygen
        
        no ATP (needed to detach myosin & actin)
        
        myosin & actin stay bonded = contracted
      - affected by degree of muscle development, level of activity before death & temp.
    - - after death, tissues break down due to the action of enzymes (autolysis)
      - loss of oxygen in tissues favours growth of anaerobic bacteria
      - affected by temp, oxygen availability, injuries (allow bacteria to enter more quickly)
    - - cooling curve
      - metabolic reactions in the body slow down and eventually stop, causing body temp. to fall until it matches the temp. of surroundings (algor mortis)
      - affected by temp, clothing, body weight, body position, humidity & wind
    - - lifecycles of these insects that colonise the body can help estimate TOD
      - affected by drugs, humidity, oxygen availability & temp
    - - community of species present when the body is found allows the stage of succession to be determined and the TOD estimated
      - affected by location of body (underground, in water, sealed away, in the open)
      - species’ found in a dead body change over time (due to conditions changing)
  - - - microorganisms feed on & break down the dead tissues
      - microorganisms secrete enzymes that break down the dead organic matter into small molecules that they can respire
    - - body’s own enzymes act on itself, breaking down cells & tissues
- - - - cell lysis – cell membrane is broken down, causes rapid cell death
      - cell fusion – infected cells fuse with neighbouring uninfected cells
      - cell transformation – change in growth, phenotype, or indefinite reproduction of cells
    - - replication of DNA, replication of plasmids, cytoplasm and cell wall splits into two
      - Generation time = time between divisions of bacteria
      - abilities of some bacterial cells include
        
        transformation – many can acquire new genes by taking up DNA molecules from their surroundings
        
        … transduction – bacterial DNA is moved between bacteria by a virus
        
        … conjugation – some bacteria can transfer their chromosome to a recipient bacteria
    - - Gram-positive bacteria
        
        stain purple
        
        have a thick cell wall
      - Gram-negative bacteria
        
        have a thin cell wall with an outer lipid layer
        
        stain pink
  - - - producing toxins – endotoxins & exotoxins released damage cells
      - damaging cell directly – use the host cell for nutrients, release waste products
      - damaging cell indirectly – can cause an immune response which inadvertently harms host cells