Infection, Immunity and Forensics

  • Created by: Emily
  • Created on: 19-01-11 13:08


  • State of body (rigor Mortis)
  • Decomposition
  • Forensic entomology (maggots, flys)


  • Personal I.D
  • Finger prints
  • Dental Records
  • DNA profiling


  • Infection ( Virus - HIV, bacteria - TB)
  • Symptoms
  • Treatments

Body Responses

  • Non specific
  • Specific immunity
  • Natural Defences
  • Vaccination

DNA PROFILING (determining father of child, forensic investigation, pedigree of animals, purity of food samples)

  • Allows us to identify biological material
  • Everyones DNA is unique because of the variety found in the sections of DNA which are not used to code for proteins (introns)
  • They look for short repeated sequences in these introns (short tandem repeats)
  • There can be up to several hundred copies of STR at a single locus - People Vary in regard to the number of these repeats they carry at each locus.
  • The STR at many loci build up a unique pattern for that individual


  • Double stranded DNA + Restriction Enzymes. DNA is cut into fragments (using restriction enzymes or the PCR. They carry a negative charge)
  • Fragments of double stranded DNA are loaded into the walls of an agarose gel in a tank.
  • The negatively charged DNA moves towards the positive electrode. These fragments seperate into individual bands
  • DNA is transferred by a nylon Membrane by solution drawn up through the gel. DNA double strands split and stick to the membrane
  • Membrane is placed in a bag with DNA probe. Single stranded DNA probe binds to fragments with a complimentary sequence.
  • Can be shown by X ray film or UV light
  • Fragments move at different rates according to their size and charge. Small fragments with fewer repeats travel faster and end up closer to the electrode after a set time.

Polymerase Chain Reaction

  • Allows small samples of DNA to be amplified so that they can be used during DNA profiling
  • Relies on: DNA primers, Short sequences of DNA adjacent to the STR)
  • A cycle of temp changes results in huge numbers of DNA fragments being produced
  • 90-95 degrees for 30 seconds - DNA strand seperates.
  • 50-60 degrees for 20 seconds - Primers bind to DNA strand
  • 75 degress for a minute - DNA polymerase builds up complimentary strands of DNA.

Determining the time of death

 Body Temperature - Body temp is usually 37 degrees but the body begins to cool straight after death. During the first 24 hours after death the temperature if the body when it is found can be used  to work out how long ago the person died.

Degree of Muscle contraction - Muscles relax and then stiffen. This stiffening is known as rigor mortis. This occurs within about 6-9 hours (depending on the temperature). The stiffness occurs because muscle contraction needs ATP  which can not be made once respiration stops, so the muscles become fixed. This stiffness wears off again after about 36 hours in cooler conditions as the muscle tissue starts to break down.

Extent of decomposition- bodies usually allow a standard pattern of decay. Enzymes in the gut start to break down the wall of the gut and…


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