✭ topic 6: immunity, infection and forensics

• how can forensic entomology be used to determine time of death?

  a known species of maggot or insect can be measured to work out how old they are.

  you can also look at what insects are present
• name a change which occurs during decomposition

  discolourisation, gas formation, bloating, gases released, body shrinkig
• name factors which can affect post-mortem cooling

  -body size

  • position
  • clothing
  • air movement
  • humidity
  • temperature of surroundings (ambient temperature)
• why are STRs used to make a DNA profile?

  the number of STRs is unique to a majority of individuals so you will be able to create a specific pattern for each person
• what chemical agents are needed during PCR?

  DNA polymerase, primers, nucleotides, enzymes, DNA sample
• what happens at temperature 55C during PCR?

  the primers attach at start of STR

  -annealing primers anneal to beginning of STR
• how are DNA bands visualised?

  using a labelled probe/UV light/Southern Blotting
• why do bonds between muscles become fixed during rigor mortis?

  respiration stops and ATP is no longer produces and the pH falls, preventing enzymes from carrying out anaerobic respiration
• state two differences between a bacteria and virus

  bacteria prokaryotic , virus is not

  bacteria has circular DNA , virus has linear DNA or RNA
• why are dental records used to identify a person?

  they last for a long term and teeth resistant to burning
• example of non-specific immune response


  skin, fever
• specific immune response

  response by lymphocytes that help to defend body against specific diseases
• lymphocytes


  white blood cells that help defend the body against specific diseases
• where do lymphocytes


  circulate in blood and lymph and gather in large numbers at site of any infection
• where are lymphocytes held

  reserve supplies of lymphocytes are held in strategically positioned lymphoid tissue
• what are the two main type of lymphocytes

  B cells and T cells
• B and T cells


  respond to antigens, proteins and other foreign chemicals
• antigens


  protein molecules (such as the ones on the surface of bacteria and virus)
• what characteristic of antigen allows lymphocytes to identify

  large size and characteristic molecule shape allow lymphocytes to identify which ones are foreign
• what is response by lymphocytes called


  specific immune response
• where are B lymphocytes produced

  in the bone marrow
• what does each B cell have

  an antigen receptor on its surface
• when is the B cell activated


  when its specific receptor binds to an antigen with the complementary shape
• what happens once the B cell is activated


  it secretes antibodies in response to the antigen
• antibodies

  special protein molecules of a class known as immunoglobulins
• where do antibodies bind

  to the antigens on the microbe cell surface membrane
• what do antibodies act as

  labels, allowing phagocytes to recognise and destroy the cell
• where does the B cell bind

  to only one specific antigen

  each different antigen will bind and activate different B cells
• activated B cell secretes antibodies

  antibodies produced bind with antigens on surface of bacteria and label them

  antibodies bind to the antibody receptor on the macrophage

  macrophage engulfs antibodies and bacteria

  lysosome in macrophage fuse with vacuole, releasing digestive enzymes that destroy bacterium
• What are T cells also known as?

  T lymphocytes
• What is the role of T cells in the immune system?

  They are involved with the specific immune response
• Where are T cells produced?

  In the bone marrow
• Where do T cells finish maturing?

  In the thymus
• What does the 'T' in T cells stand for?

  Thymus
• What are the specific cell surface receptors on mature T cells called?

  T cell receptors
• How do T cell receptors compare to antibodies?

  They have a similar structure
• What is the specificity of T cell receptors?

  Each is specific to a particular type of antigen