infection, immunity and forensics Flashcards
How are molecules such as carbon dioxide and methane produced during decomposition?
- when plants/animals die, microorganisms on them secrete enzymes that decompose organic matter into small molecules
- when the microorganisms respire, they produce these molecules
state the ways in which time of death can be estimated?
- body temp
- degree of muscle contraction
- forensic entomology
- extent of decomposition
- stage of succession
Outline the procedure for PCR
- DNA sample, free nucleotides, primers and DNA polymerase heated to 95 degrees to break open the DNA
- the mixture is cooled to 50 degrees to allow primers to bind
- heated to 72 degrees to allow DNA polymerase to link free DNA nucleotides with the template strand
outline the procedure for gel eletrophoresis
- DNA is placed into a well of an agarose tank, and covered w buffer
- electric current is passed through- DNA move towards anode
- fragments separate according to length
name two of HIV’s evasion mechanisms
any of:
- kills immune system cells it infects
- high rate of mutation (antigenic variation) -> new primary response every time
- disrupts antigen presentation
name two of TB’s evasion mechanisms
- produces substances which prevent the lysosome fusing with the phagocytic vacuole
- disrupts antigen presentation
describe how antibiotics work to inhibit bacterial metabolism
- inhibit enzymes which are needed to make chemical bonds in cell walls -> cell bursts due to increased pressure from osmosis
- binds to bacterial ribosomes, inhibiting protein production (cant make enzymes)
briefly describe aseptic technique
- regularly disinfect surfaces
- work near bunsen burner
- sterilising wire inoculation loop by passing through flame before and after use
identify two methods of reducing the frequency of HAIs:
- hospital staff encouraged to wash hands
- people with HAIs moved to isolation ward
explain how the stage of succession on a body is changed with time
- immediately after death, conditions favourable for bacteria
- bacteria decompose tissues, conditions become favourable for flies
- etc.
- eventually, no tissues remain and conditions are not favourable for any organisms
why does rigor mortis occur?
- muscle cells deprived of O2 -> anaerobic respiration produced lactic acid
- conditions become more acidic, inhibits enzymes which produce ATP
- bonds between myosin and actin are fixed
what is the constant region of antibodies responsible for?
binding to receptor sites on the immune system cells
list 3 ways in which antibodies protect the body from pathogens
- agglunating pathogens
- preventing pathogens from binding to human cells
- neutralising toxins
what is meant by ‘agglunating pathogens’?
each antibody has two binding sites, this means an antibody can bind to two pathogens at once.
-pathogens get clumped together and destroyed
what is the difference between excreted and membrane bound antibodies?
-membrane bound antibodies contain an extra section of protein that anchors it into the B cell
what is splicing?
a post transcriptional change in which introns are removed from pre-mRNA
what is alternative splicing? How does it give rise to multiple proteins from the same gene?
- exons (coding blocks) are removed instead of introns
- this means the base sequence of the mRNA is different
- and the structure of produced protein is modified
what does the primary response refer to?
when the body is exposed to pathogens, activating the specific and non-specific responses
why is the secondary immune response quicker?
T + B memory cells produced in the primary response can quickly divide into T killer cells and correct plasma cells, secreting antibodies
what is the difference between active immunity and passive immunity?
- active immunity takes a while to develop and is long lasting
- whereas passive immunity is immediate and short-term
what is meant by the ‘evolutionary race’ between pathogens and their hosts?
- hosts evolve to have better immune systems
- pathogens evolve to have better evasion mechanisms
what is antigenic variation?
when genes that code for antigen proteins are mutated, changing the structure of the antigens, so they are not recognised by the body
