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forensics immunity and infection Flashcards

1
Q

what does gel electrophoresis produce?

A

a pattern of bands on the gel that represent DNA fragments of different length

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2
Q

what is the purpose of southern blotting?

A

to detect the presence of certain DNA sequences in a given genome

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3
Q

why do different sized molecules move through the gel at different rates? (gel electrophoresis)

A

pores in the gel allow smaller molecules to move quickly, but larger molecules move slower

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4
Q

in gel electrophoresis does DNA move towards the anode or the cathode and why?

A

the anode because DNA is negatively charged due to the presence of phosphate groups

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5
Q

what do PCR reactions require?

A

DNA/RNA to be amplified
primers
DNA polymerase
free nucleotides
buffer solution

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6
Q

what is a primer?

A

short sequence of single stranded DNA
have base sequences complimentary to 3’ end of DNA
define region that is to be amplified
identifying where DNA polymerase needs to bind

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7
Q

why is DNA polymerase suitable for PCR?

A

does not denature at high temps required during first stage

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8
Q

what is the purpose of the buffer solution in PCR?

A

ensures the optimum pH for reactions

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9
Q

what are the stages of PCR?

A

denaturation
annealing
elongation/ extension

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10
Q

explain the denaturation stage of PCR

A

double stranded DNA heated to 95ºC
breaks H bonds between strands

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11
Q

explain the annealing stage of PCR

A

50-60ºC
so primers can join to complimentary bases at the end of the single strands

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12
Q

explain the elongation/ extension stage of PCR

A

72ºC
optimum temp for polymerase to build complimentary strands of DNA to produce new identical double stranded DNA molecules

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13
Q

what can be analysed to determine the time since death?

A

core body temperature
degree of rigor mortis
state of decomposition
entomology

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14
Q

explain core body temp and time since death

A

heat from respiration and other metabolic reactions needed to maintain body temp around 37ºC

metabolic reactions end at death so no more heat produced so body temp drops to temp of surrounding environment

decreases by 1.5-2ºC per hour

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15
Q

what conditions affect the rate at which body heat is lost?

A

air temperature
sa: vol
presence of clothing

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16
Q

explain rigor mortis and time since death

A

no more oxygen reaches muscle cells after death so they respire anaerobically and produce lactic acid

lactic acid decreases muscle cell pH, denaturing enzymes that produce ATP

without ATP myosin heads cannot be released from actin filaments, locking muscles in a contracted state

begins in smaller muscles in head and ends in larger muscles of lower body

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17
Q

what affects the rate of rigor mortis?

A

high temp speeds up rate
level of muscle development

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18
Q

h

A
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19
Q

explain state of decomposition and time since death

A

carried out by decomposers- enzymes secreted from their cells break down biological molecules in dead tissue

break down cells/ tissues in few days- greenish skin

breakdown tissues/ organs in few weeks- produces gases eg methane which lead to bloating and sulphur which stinks. skin blisters and falls off body

soft tissues turn into liquid and leave body

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20
Q

what factors affect the rate of decomposition?

A

slower at lower temp, faster at higher
slower in anaerobic conditions

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21
Q

what are examples of decomposers?

A

bacteria
fungi

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22
Q

explain entomology and time since death

A

dead bodies provide ideal habitats for many insect species
entomology is the study of those insect colonies
diff species present at diff times after death
eg flies a few hours after but beetles later
blowfly eggs hatch after 24h so if larvae r present, it indicates that TOD was over 24h ago

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23
Q

what factors affect the progression of insect life cycles on dead bodies?

A

drugs present in the body
humidity of surroundings
oxygen availability
temperature

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24
Q

how is succession different in forensics than ecology?

A

in an ecosystem, pioneer species are out-competed and disappear as a system matures
in a dead body they stay as decomposition progresses

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25
Q

what factors affect succession on dead bodies

A

location such as underwater, buried in a coffin or soil
as insect accessibility and oxygen availability differ

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26
Q

what are the main ways that pathogens can enter the body?

A

broken skin- direct access to tissues and bloodstream
digestive system- when consuming contaminated food and drink
respiratory system- inhaling
mucosal surfaces- lining of body cavities eg nose, mouth, genitals

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27
Q

how is skin a barrier to infection?

A

physical barrier
if damaged, leaves exposed tissue vulnerable to pathogens
blood clotting prevents pathogen entry if skin damage but takes time so some pathogens could enter before blood clots form

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28
Q

how are microorganisms of the gut and skin barriers to infection?

A

compete with pathogens for resources, limiting the number of pathogens, limiting pathogen ability to infect body

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29
Q

how is stomach acid a barrier to infection?

A

HCl creates acidic environment which is unfavourable to pathogens present on food and drink

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30
Q

how is lysozyme a barrier to infection?

A

secretions of mucosal surfaces (eg tears, saliva, mucus) contain an enzyme called lysozyme
enzyme damages bacterial cell walls, causing the cells to burst

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31
Q

what is a non specific immune response?

A

has the same response regardless of which pathogen enters

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32
Q

what is a specific immune response?

A

immune system recognises specific pathogens due to presence of antigens on their cell surface

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33
Q

what are antigens?

A

proteins/ glycoproteins
identify a cell as self or non self
pathogens have non self

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34
Q

what is inflammation?

A

*surrounding area of a wound becomes swollen, warm, painful
*body cells called mast cells respond to tissue damage by secreting histamine
*histamine stimulates: vasodilation increases blood flow through capillaries
cap walls become more permeable allowing fluid to enter tissues to create swelling and some plasma proteins leave the blood
phagocytes leave blood and enter tissue to engulf foreign particles
cells release cytokines

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35
Q

what is histamine?

A

chemical signalling molecule
enables cell signalling or communication between cells

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36
Q

what are cytokines?

A

signalling molecule
triggers immune response in infected area

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37
Q

what are interferons?

A

cells infected by viruses produce anti viral proteins called interferons which prevent viruses from spreading to uninfected cells

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38
Q

how do interferons work?

A

*inhibit production of viral proteins, preventing virus from replicating
*activate wbc involved w specific immune response to destroy infected cells
*increase non specific immune response eg promoting inflammation

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39
Q

what are phagocytes?

A

*type of wbc responsible for removing dead cells and invasive microorganisms by phagocytosis
*travel thru body and leave blood by squeezing thru cap walls
*released in large numbers during infection

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40
Q

what is the process of phagocytosis?

A

*pathogens and body cells under attack release chemicals eg histamine, which attract phagocytes to the site where pathogens are
*phagocytes recognise antigens on pathogen as being non self
*cell surface membrane of phagocyte extends out and around pathogen, engulfing it and trapping it in a phagocytic vacuole (endocytosis)
*digestive enzymes eg lysozyme released into phagocytic vacuole when lysosomes fuse w it, and digest the pathogen
*phagocyte presents antigen of pathogen on its cell surface membrane and becomes an antigen presenting cell, which initiates specific immune response

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41
Q

what is a bacterial cell wall made from?

A

murein

42
Q

what is the role of the capsule in bacterial cells?

A

helps protect bac from drying out
protects from attack by other cells of immune system

43
Q

what is the flagellum in bacterial cells?

A

long tail like structures
rotate
enabling prokaryote to move

44
Q

what is the pili in bacterial cells?

A

thread like structures on surface
enable bac to attach to other cells/ surfaces
involved in gene transfer during sexual reproduction

45
Q

how can viruses reproduce?

A

infecting living cells and using their protein building machinery to produce new viral particles

46
Q

what are some structures in viruses?

A

nucleic acid core
protein coat called a capsid
outer layer called envelope formed from membrane phospholipids of cell they were made in
attachment proteins

47
Q

what bacteria causes the disease tuberculosis?

A

mycobacterium tuberculosis

48
Q

how is TB transmitted?

A

infected ppl cough/ sneeze
bac enter air in droplets released from lungs
uninfected ppl inhale them

49
Q

what happens when TB is engulfed by phagocytes in the lungs?

A

bac may be able to survive and reproduce inside phagocytes
individuals w healthy immune system dont develop TB at this stage

50
Q

what happens to the TB phagocytes over time?

A

encased in structures called tubercles
bac remains dormant

51
Q

what is the active phase of TB?

A

bac may become activated and overpower immune system at a later stage

52
Q

what are the first symptoms of TB?

A

fever
fatigue
coughing
lung inflammation

53
Q

what could happen if TB is left untreated?

A

bac cause extensive damage to lungs
respiratory failure leads to possible death
can spread to other body parts so possible organ failure

54
Q

what type of proteins are antibodies?

A

globular

55
Q

what do antibodies bind to antigens on pathogens to do?

A

block binding receptors
act as anti toxins by binding to toxins produced by pathogens
cause pathogens to clump together

56
Q

what are the parts of an antibody?

A

constant region
variable region
disulphate bridges
heavy chains
light chains
antigen binding site
hinge region

57
Q

where are T cells produced?

A

bone marrow

58
Q

where do T cells mature?

A

thymus

59
Q

when are T cells activated?

A

when they bind to their specific antigen on the surface of an apc

60
Q

what happens to T cells after they are activated?

A

divide by mitosis and differentiate into: T helper, T killer, T memory

61
Q

what is the function of T helper cells?

A

release chemical signalling molecules to help activate B cells

62
Q

what is the function of T killer cells?

A

bind to and destroy any apc

63
Q

what is the function of T memory cells?

A

remain in blood
enable faster specific immune response if same pathogens encountered again

64
Q

where are B cells produces and mature?

A

bone marrow

65
Q

how are B cells activated?

A

binding of B cell to specific antigen
cell signalling molecules produced by T helper cells

66
Q

what happens once B cells are activated?

A

divide repeatedly by mitosis producing many clones
daughter cells differentiate into: effector cells, memory cells

67
Q

what are the role of effector cells?

A

go on to form plasma cells
which produce specific antibodies that combine w antigen that entered body

68
Q

what are the types of immunity?

A

active natural
active artificial
passive natural
passive artificial

69
Q

what is the difference between the secondary and primary immune response?

A

secondary has memory cells produced in primary so
antibodies produced faster
in higher conc
eliminates pathogen before symptoms show

70
Q

how do active immune responses occur?

A

antigen enters body triggering a specific immune response
memory cells produced so long term immunity

71
Q

how do passive immune responses occur?

A

no immune response, antibodies gained from another source, not the infected person
no memory cells that can enable secondary response

72
Q

what causes active natural immunity?

A

exposure to pathogens

73
Q

what causes active artificial immunity?

A

vaccinations

74
Q

what causes passive natural immunity?

A

babies- antibodies from breastmilk
foetuses- antibodies across placenta from mum

75
Q

what causes passive artificial immunity?

A

injection/ tranfusion of antibodies collected from ppl/ animals whose immune system had been triggered by a vax to produce antibodies

76
Q

what do vaccines contain?

A

dead/ weakened form of pathogen
antigens alone
less harmful strains of pathogen
genetic material that codes for antigens

77
Q

antigenic variation:

A

vax needs to be constantly modified to keep up with the pathogen’s antigens mutating

78
Q

what is a retrovirus?

A

a virus that can make DNA from RNA because they have reverse transcriptase

79
Q

what is inside the core of HIV?

A

integrase
RNA
reverse transcriptase

80
Q

what glycoprotein receptors do HIV have?

A

gp120
co receptor

81
Q

how can HIV be transmitted in body fluids?

A

sexual intercourse
blood donation
mum to kid across placenta
breastmilk
sharing needles for intravenous drugs
mixing of blood between mum and kid during birth

82
Q

what is the chronic phase of HIV?

A

no symptoms
years/ months

83
Q

what symptoms occur immediately after HIV infection?

A

mild flu like

84
Q

when does HIV develop into AIDS?

A

constant opportunistic infections
T helper cells drop below a critical level

85
Q

what are opportunistic diseases?

A

diseases that would usually cause minor issues in healthy ppl
eg TB

86
Q

what factors effect how quickly HIV progresses into AIDS, and how long a person w AIDS survives?

A

age
strain of HIV
access to healthcare
number of existing infections

87
Q

what are introns

A

non coding sections of DNA
found in genes

88
Q

what are exons

A

coding sections of DNA

89
Q

what is splicing

A

during transcription both introns and exons are transcribed and pre-mRNA produced
before pre-mRNA leaves the nucleus
introns removed
exons joined together

90
Q

what is alternative splicing

A

exons can be spliced in many diff ways
produce diff mature mRNA molecules
so a single eukaryotic gene can code for more than one polypeptide chain

91
Q

what are antibiotics?

A

chemical substances that damage bacterial cells, with little or no harm to human tissue

92
Q

what are the types of antibiotics?

A

bactericidal: kill bacterial cells
bacteriostatic: inhibit bacterium growth processes (high doses do kill)

93
Q

how do antibiotics work?

A

inhibiting bacterial enzymes needed to form bonds in cell walls, prevents bac growth, death as cell walls weakened and burst under pressure of water entering by osmosis

bind to ribosomes and prevent protein synthesis so no enzymes produced so no metabolic processes

damage cell membranes so loss of useful metabolites or uncontrolled water entry

preventing bac DNA from coiling into rings so it no longer fits into bac cell

94
Q

why are mammalian cells not damaged by antibiotics?

A

eukaryotic
no cell wall
diff enzymes
diff ribosomes

95
Q

why are viruses not damaged by antibiotics?

A

no cellular structures eg
enzymes
ribosomes
cell walls

96
Q

what is a hospital acquired infection (HAI) ?

A

infections contracted by patients while in hospital

97
Q

what are some hospital measures to reduce HAI spread?

A

regular hand washing
quarantine of ppl w HAI
surfaces and equipment disinfected after every use

98
Q

why is the risk of antibiotic resistant strains of bacteria arising high in hospitals?

A

antibiotics widely used in hospitals
which is a selection pressure for resistant stains to develop

99
Q

what are practices in hospitals to reduce the risk of antibiotic resistant HAIs?

A

no antibiotics prescribed for viruses or minor infections
no antibiotics as a preventative measure
narrow spectrum antibiotics prescribed
rotate use of diff antibiotics

100
Q

how many strands of rna does hiv have

A

2

101
Q

in gel electrophoresis, do DNA fragments move towards the cathode or the anode

A

anode

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