T6: Immunity, Infections & Forensics

• What is the primary method for determining the time of death of a mammal?

  By examining the extent of decomposition, forensic entomology, body temperature, and degree of muscle contraction.
• What are the factors used to determine the time of death in mammals?

  • Extent of decomposition
  • Forensic entomology
  • Body temperature
  • Degree of muscle contraction
• How does the extent of decomposition help in determining the time of death?

  It indicates how long a body has been dead based on the pattern of decay.
• What is forensic entomology?

  It is the study of insects to determine the time of death.
• Why is the age of insects present at a crime scene important?

  It helps to estimate the time of death based on the specific life cycles of insect species.
• How does the stage of succession relate to time of death?

  Different species colonize the body at various stages of decay, which can indicate the time of death.
• What happens to body temperature after death?

  It begins to decrease as metabolic reactions stop.
• Why can body temperature only be used to determine time of death within the first 24 hours?

  Because the body eventually reaches the temperature of its surroundings.
• What factors can affect the rate of body temperature decrease after death?

  Size of the body, covering, and weather conditions.
• What is rigor mortis?

  It is the stiffening of muscles after death due to ATP depletion and calcium ion buildup.
• When does rigor mortis begin after death?

  It begins around 2-4 hours after death.
• How long does rigor mortis last?

  It lasts for about 36 hours.
• What role do microorganisms play in decomposition?

  They decompose organic matter and recycle carbon by breaking it down into smaller molecules.
• What are introns and exons in DNA?

  Introns are non-coding regions, while exons are coding regions of DNA.
• What are short-tandem repeats?

  They are repeating base sequences found in introns.
• What is the purpose of Polymerase Chain Reaction (PCR)?

  To amplify a DNA sample before analysis.
• What are the steps involved in the Polymerase Chain Reaction (PCR)?

  1. Set up a reaction mixture with DNA sample, primers, free nucleotides, and DNA polymerase.
  2. Heat to 95°C to separate DNA strands.
  3. Cool to 50-65°C for primers to bind.
  4. Increase temperature to 70°C for DNA polymerase to create copies.
  5. Repeat the cycle to amplify DNA.
• What is gel electrophoresis used for in DNA profiling?

  To separate and visualize the amplified DNA sample.
• What are the steps involved in gel electrophoresis?

  1. Cut DNA fragments with restriction endonuclease enzymes.
  2. Place fragments in agarose gels and dye with ethidium bromide.
  3. Apply current to the gel to separate fragments by size.
  4. Place a filter on top to draw DNA fragments to it.
  5. Add gene probes for hybridization and visualize results.
• What are mini/microsatellites in DNA?

  They are repeated sequences of DNA in introns, varying in size.
• What are the main components of a virus?

  A nucleic acid (DNA or RNA) and a protein coat called the capsid.
• How do bacteria differ from viruses?

  Bacteria are prokaryotes with no membrane-bound organelles, while viruses consist only of nucleic acid and a protein coat.
• Why are viruses not classified as living organisms?

  Because they cannot carry out the processes that define living organisms and depend entirely on hosts for survival.
• What is an example of a bacterial disease?

  Tuberculosis (TB).
• What happens during the first infection of tuberculosis?

  It may be symptomless, and infected phagocytes are sealed in tubercles in the lungs.
• How do tubercles protect bacteria in tuberculosis?

  They are covered with a thick waxy coat that prevents destruction by the immune system.
• What are the symptoms of active tuberculosis?

  Breathing problems, coughing, weight loss, and fever.
• How can tuberculosis spread in the body?

  It can spread to other areas of the body when the immune system is weakened.
• What is an example of a viral infection?

  Human Immunodeficiency Virus (HIV).
• What are the first symptoms of HIV?

  Flu-like symptoms including fevers, tiredness, and headaches.
• What happens after HIV antibodies appear in the blood?

  The symptoms may disappear until the immune system weakens again, leading to AIDS.
• What are the symptoms of AIDS?

  Weight loss, diarrhea, dementia, cancers, and opportunistic infections like TB.
• What are the physical barriers to infection?

  • Skin: tough barrier made of keratin.
  • Stomach acid: kills bacteria.
  • Gut and skin flora: competes with pathogens for resources.
• What is a non-specific response to infection?

  It is a response that does not require recognition of antigens and includes inflammation, fever, lysozyme action, and phagocytosis.
• What occurs during inflammation as a non-specific response?

  Histamines cause vasodilation, increasing blood flow and permeability to help destroy pathogens.
• How does fever act as a non-specific response to infection?

  It raises body temperature to increase enzyme reaction rates and decrease pathogen reproduction.
• What is the role of lysozyme in the immune response?

  Lysozyme kills bacterial cells by damaging their cell walls.
• What is phagocytosis?

  It is the process by which white blood cells engulf and destroy pathogens.
• What are the key differences between bacteria and viruses?

  • Bacteria are prokaryotes; viruses are not living organisms.
  • Bacteria have a cell structure; viruses do not.
  • Bacteria can survive independently; viruses require a host.
  • Bacteria are larger than viruses.
• What is released by damaged white vessels that causes vasodilation?

  Histamines