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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
what factors affect succession on dead bodies
location such as underwater, buried in a coffin or soil as insect accessibility and oxygen availability differ
26
what are the main ways that pathogens can enter the body?
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
27
how is skin a barrier to infection?
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
28
how are microorganisms of the gut and skin barriers to infection?
compete with pathogens for resources, limiting the number of pathogens, limiting pathogen ability to infect body
29
how is stomach acid a barrier to infection?
HCl creates acidic environment which is unfavourable to pathogens present on food and drink
30
how is lysozyme a barrier to infection?
secretions of mucosal surfaces (eg tears, saliva, mucus) contain an enzyme called lysozyme enzyme damages bacterial cell walls, causing the cells to burst
31
what is a non specific immune response?
has the same response regardless of which pathogen enters
32
what is a specific immune response?
immune system recognises specific pathogens due to presence of antigens on their cell surface
33
what are antigens?
proteins/ glycoproteins identify a cell as self or non self pathogens have non self
34
what is inflammation?
*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
35
what is histamine?
chemical signalling molecule enables cell signalling or communication between cells
36
what are cytokines?
signalling molecule triggers immune response in infected area
37
what are interferons?
cells infected by viruses produce anti viral proteins called interferons which prevent viruses from spreading to uninfected cells
38
how do interferons work?
*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
39
what are phagocytes?
*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
40
what is the process of phagocytosis?
*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
41
what is a bacterial cell wall made from?
murein
42
what is the role of the capsule in bacterial cells?
helps protect bac from drying out protects from attack by other cells of immune system
43
what is the flagellum in bacterial cells?
long tail like structures rotate enabling prokaryote to move
44
what is the pili in bacterial cells?
thread like structures on surface enable bac to attach to other cells/ surfaces involved in gene transfer during sexual reproduction
45
how can viruses reproduce?
infecting living cells and using their protein building machinery to produce new viral particles
46
what are some structures in viruses?
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
what bacteria causes the disease tuberculosis?
mycobacterium tuberculosis
48
how is TB transmitted?
infected ppl cough/ sneeze bac enter air in droplets released from lungs uninfected ppl inhale them
49
what happens when TB is engulfed by phagocytes in the lungs?
bac may be able to survive and reproduce inside phagocytes individuals w healthy immune system dont develop TB at this stage
50
what happens to the TB phagocytes over time?
encased in structures called tubercles bac remains dormant
51
what is the active phase of TB?
bac may become activated and overpower immune system at a later stage
52
what are the first symptoms of TB?
fever fatigue coughing lung inflammation
53
what could happen if TB is left untreated?
bac cause extensive damage to lungs respiratory failure leads to possible death can spread to other body parts so possible organ failure
54
what type of proteins are antibodies?
globular
55
what do antibodies bind to antigens on pathogens to do?
block binding receptors act as anti toxins by binding to toxins produced by pathogens cause pathogens to clump together
56
what are the parts of an antibody?
constant region variable region disulphate bridges heavy chains light chains antigen binding site hinge region
57
where are T cells produced?
bone marrow
58
where do T cells mature?
thymus
59
when are T cells activated?
when they bind to their specific antigen on the surface of an apc
60
what happens to T cells after they are activated?
divide by mitosis and differentiate into: T helper, T killer, T memory
61
what is the function of T helper cells?
release chemical signalling molecules to help activate B cells
62
what is the function of T killer cells?
bind to and destroy any apc
63
what is the function of T memory cells?
remain in blood enable faster specific immune response if same pathogens encountered again
64
where are B cells produces and mature?
bone marrow
65
how are B cells activated?
binding of B cell to specific antigen cell signalling molecules produced by T helper cells
66
what happens once B cells are activated?
divide repeatedly by mitosis producing many clones daughter cells differentiate into: effector cells, memory cells
67
what are the role of effector cells?
go on to form plasma cells which produce specific antibodies that combine w antigen that entered body
68
what are the types of immunity?
active natural active artificial passive natural passive artificial
69
what is the difference between the secondary and primary immune response?
secondary has memory cells produced in primary so antibodies produced faster in higher conc eliminates pathogen before symptoms show
70
how do active immune responses occur?
antigen enters body triggering a specific immune response memory cells produced so long term immunity
71
how do passive immune responses occur?
no immune response, antibodies gained from another source, not the infected person no memory cells that can enable secondary response
72
what causes active natural immunity?
exposure to pathogens
73
what causes active artificial immunity?
vaccinations
74
what causes passive natural immunity?
babies- antibodies from breastmilk foetuses- antibodies across placenta from mum
75
what causes passive artificial immunity?
injection/ tranfusion of antibodies collected from ppl/ animals whose immune system had been triggered by a vax to produce antibodies
76
what do vaccines contain?
dead/ weakened form of pathogen antigens alone less harmful strains of pathogen genetic material that codes for antigens
77
antigenic variation:
vax needs to be constantly modified to keep up with the pathogen's antigens mutating
78
what is a retrovirus?
a virus that can make DNA from RNA because they have reverse transcriptase
79
what is inside the core of HIV?
integrase RNA reverse transcriptase
80
what glycoprotein receptors do HIV have?
gp120 co receptor
81
how can HIV be transmitted in body fluids?
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
what is the chronic phase of HIV?
no symptoms years/ months
83
what symptoms occur immediately after HIV infection?
mild flu like
84
when does HIV develop into AIDS?
constant opportunistic infections T helper cells drop below a critical level
85
what are opportunistic diseases?
diseases that would usually cause minor issues in healthy ppl eg TB
86
what factors effect how quickly HIV progresses into AIDS, and how long a person w AIDS survives?
age strain of HIV access to healthcare number of existing infections
87
what are introns
non coding sections of DNA found in genes
88
what are exons
coding sections of DNA
89
what is splicing
during transcription both introns and exons are transcribed and pre-mRNA produced before pre-mRNA leaves the nucleus introns removed exons joined together
90
what is alternative splicing
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
what are antibiotics?
chemical substances that damage bacterial cells, with little or no harm to human tissue
92
what are the types of antibiotics?
bactericidal: kill bacterial cells bacteriostatic: inhibit bacterium growth processes (high doses do kill)
93
how do antibiotics work?
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
why are mammalian cells not damaged by antibiotics?
eukaryotic no cell wall diff enzymes diff ribosomes
95
why are viruses not damaged by antibiotics?
no cellular structures eg enzymes ribosomes cell walls
96
what is a hospital acquired infection (HAI) ?
infections contracted by patients while in hospital
97
what are some hospital measures to reduce HAI spread?
regular hand washing quarantine of ppl w HAI surfaces and equipment disinfected after every use
98
why is the risk of antibiotic resistant strains of bacteria arising high in hospitals?
antibiotics widely used in hospitals which is a selection pressure for resistant stains to develop
99
what are practices in hospitals to reduce the risk of antibiotic resistant HAIs?
no antibiotics prescribed for viruses or minor infections no antibiotics as a preventative measure narrow spectrum antibiotics prescribed rotate use of diff antibiotics
100
how many strands of rna does hiv have
2
101
in gel electrophoresis, do DNA fragments move towards the cathode or the anode
anode

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