Topic 6 - Disease and Forensics Flashcards
(129 cards)
1
Q
What is the name of the glycoprotein on HIV?
A
gp120
2
Q
What does gp120 bind to?
A
A cd4 receptor on a T helper cells(lymphocytes)
3
Q
Why is unbroken skin a barrier to HIV?
A
Keratin in skin surface forms a hard, impenetrable, physical barrier.
4
Q
What is an enzyme’s structure?
A
An enzyme is a globular protein.
It has an active site and charged R groups on outside of molecules - specifically hydrophilic on the outside.
5
Q
How could HIV drugs work?
A
- HIV drugs would prevent viral replication so T helper cells will not be burst by virus particles leaving the cell.
- Inhibition of reverse transcriptase so DNA could not be made from viral RNA.
- Inhibition of integrase by drugs so viral DNA cannot integrate into host DNA.
6
Q
HIV genetic material?
A
RNA
Linear nucleic acid
No plasmids
7
Q
Mycobacterium tuberculosis genetic material?
A
DNA
Circular nucleic acid
Plasmids
8
Q
How do macrophages act as APCs?
A
Macrophages present antigens to T helper cells. The macrophage binds to T helper cell by CD4 receptors on T cell and by MHC (major histocompatibility complex) on macrophages.
9
Q
T helper lymphocyte decrease: the effect on other blood components? (In HIV)
A
B cells are not activated meaning fewer antibodies. T killer cells increase.
10
Q
Change in CD4 T-lymphocytes during HIV and decrease after HIV infection.
A
Gp120 in virus binds with CD4 receptors in surface membrane of lymphocyte. Viral RNA enters the lymphocyte and is used to produce viral DNA by action of reverse transcriptase to form new viruses. Lymphocyte is destroyed when new viruses bud out of cell.
11
Q
Changes in number of CD4 T-lymphocytes during first six weeks after infection with HIV.
A
Numbers decrease.
Small decrease in first week and between 4-6 weeks.
Large decrease between weeks 2 to 3.
Credit use of manipulated figures.
12
Q
TB vs. Hosts in an evolutionary race
Affecting APC affecting T cell helper cells
A
Mutation has occurred in the DNA
There is a change in antigen of bacteria. Memory T cells will not recognise the new antigen. Another primary immune response is needed. E.g. New antigen needs to be presented to the T helper cells to activate another population of T helper cells. Phagocytes/ macrophages unable to recognise, engulf, and destroy bacteria. Antigen presentation is not possible.
13
Q
Why antibody B not present after infection?
A
If antibodies will only be present if antigen is present, antigen H is not present in vaccine. Vaccination failed to stimulate immune response.
14
Q
Organism in a pond
Surrounded by fast-growing trees
Allele frequency
A
Mutant allele increases, normal decreases
Reproductive success of mutant/non-photosynthetic individuals.
As trees develop, pond will be more shaded. Less light means less photosynthesis is possible. Photosynthetic individuals die and non-photosynthetic survive to pass on allele by using organic compounds - more in nutrients in pond.
15
Q
Phagocytosis and lysozyme in APCs(macrophages)
A
Bacteria have to be taken into macrophages.
Fusion of phagosome with lysosome.
Phagosome are broken down by enzymes. (E.g protease - not lysozyme as mentioned in stem of question)
Part of the pathogen has to be on membrane of macrophage.
16
Q
Type of immunity that results in production of antibody after infection?
A
Natural active immunity
17
Q
Secondary immune response
A
On infection - second exposure - memory cells are activated, cloned, and stimulated. B me merit cells differentiate into plasma cells. In secondary response, antibodies are released from plasma cells.
18
Q
Antibody A after vaccination vs. After infection
A
Levels of antibody rise sooner, faster and higher, after infection
19
Q
The name of the enzyme used in the process to amplify DNA sample
A
Polymerase
20
Q
The process that could be used to separate DNA fragments to create DNA profiles
A
Electrophoresis
21
Q
Which suspect based on DNA profiles?
A
Suspect which matches all of the trends I’m the sample.
DNA profiling assumes every individual’s DNA is unique apart from identical twins.
DNA profiling analyses the introns (non-coding blocks) (short tandem repeats)
Non-coding DNA is hypervariable large
Larger number of introns
Many combinations at each locus.
22
Q
DNA profiling evidence not absolutely conclusive.
A
DNA profiling has several different stages
Contamination can arise at any stage
Only a few sequences ( a small portion) of DNA is analysed. Possibility of two identical profiles from unrelated individuals. Identical twins or closely related individuals may also show same profile.
23
Q
Suggest how DNA profiling could be useful to scientist who examine fossils of animals and plants.
A
Comparisons can be made between DNA from fossils and other organisms to find genetic relationships (how closely related) and therefore can be used opinion taxonomy/classification. These comparisons can also be used to understand evolutionary lines and to determining common ancestor.
24
Q
Comment on reliability of data. No indication of no. Rats used No data pints No error bars in graph No indication of variability No statistical evidence No indication of experimental details, control variables. Or control group. Mean
A
A comment cannot be made
Caution should be taken in interpreting results.
Mean has been used so there must have been some repeats
25
DNA profiling
Source of DNA sample ,e.g. blood, saliva, semen
Multiple copies of DNA made using PCR (polymerase chain reaction).
Step 1:90'C
Step 2:50'C
Step 3:70'C
Use of primers, DNA polymerase, nucleotides, and many repetitions.
Restriction enzymes are used to produce DNA fragments for gel electrophoresis.
The DNA is loaded onto the gel ( agarose sugar). An electric current is applied.
Use of dye/ fluorescent tag/ UV light or use of radioactive markers and X-Ray film.
Comparisons of DNA profiles: compare total number of bands, position of bands, and size/width of bands.
26
Comparisons of DNA profiles
Compare total number of bands, position of bands, and size/width of bands.
27
Sharing Scientific Research
Scientific/peer-reviewed journals
Scientific conferences
Media reports e.g TC, radio, newspaper, Internet
28
Template stand of DNA
AAC TAG TTG GCA AGT GT GGT CAC
Could this be used in translation?
Could strand mRNA be synthesised from this?
Codes for 7 amino acid in protein synthesis?
AAC TAG TTG GCA AGT GT GGT CAC
Could this be used in translation? NO
Could strand mRNA be synthesised from this? YES
Codes for 7 amino acid in protein synthesis? YES
29
Where would the polypeptide chain of this enzyme be synthesised?
At the ribosome in the rough endoplasmic reticulum.
A ribosome/polysome consists of rRNA, protein component, and 1 large and 1 small subunit ( 2 subunits total).
RER: a ribosome attached to the membrane.
30
Gene mutation?
Change in DNA.
Change of bases/nucleotides.
This change could be a deletion, addition, duplication or substitution.
31
HIV infect B lymphocytes. True or false.
False. T (helper) lymphocytes - not B lymphocytes.
32
Do viruses have a cytoplasm?
No. Bacteria have a cytoplasm, but viruses do not.
33
Are protein capsids in bacteria?
No. Protein capsids are in viruses only.
34
B + T cells are formed in the...?
Bone marrow
35
B cells stimulate T cells to produce clones of memory cells. True or false.
False. T cells stimulate B cells to produce antibodies.
36
T helper cells so not produce chemicals that destroy pathogens. True or false.
True. T killer cells produce chemicals that destroy pathogens.
37
How do B + T cells produce clones.
Clones are produced via mitosis..
38
Why may you not see bacteria under a microscope?
Too small : limitation due to magnification or resolution.
Bacteria not stained.
Bacteria already destroyed.
Bacteria are not present in the blood e.g. Only a small sample shown.
39
How do lymphocyte numbers change during antibiotic treatment?
Fewer lymphocytes: no longer needed as antibiotics kill bacteria.
More lymphocytes: due to clinal expansion of lymphocytes as the antibiotics have not killed all the bacteria yet.
40
Placebo antibiotic effect on bacteria and lymphocyte numbers?
Placebo antibiotic has no effect therefore there will be more bacteria and lymphocytes due to clonal expansion.
41
Eukaryotic exclusive features?
A chloroplast and a nucleus are exclusive to eukaryotes (membrane-bound subunits and organelles)
42
A cell wall and a cytoplasm - eukaryotic or prokaryotic.
Both. A cell wall and a cytoplasm - eukaryotic AND prokaryotic.
43
DNA bases
Adenine
Cytosine
Guanine
Thymine
44
RNA bases
Adenine
Cytosine
Guanine
Uracil
45
Adenine or adenosine?
Adenine is the base in nucleic acid.
| Adenosine is in ATP: adenosine triphosphate
46
Explain 'triplet code'
Each amino acid is coded for by three bases.
AAT AAC CAG CAG TTT
gives four amino acids
47
Explain 'Non - overlapping' code
Each triplet is discrete
Distinct triplet codes
AAT AAC CAG CAG TTT
48
Explain 'degenerate code'
More than one code can be used for a particular amino acid or stop code. Eg. Both AAT and AAC code for leucine.
49
A mononucelotide consists of...
A phosphate group, deoxyribose, and a base.
50
Translation of the mRNA of this DNA section to polypeptide molecule.
AAT AAC CAG TTT
UUA UUG GUC AAA is the sequence of the mRNA.
A ribosome is involved and is the site of translation.
Each tRNA molecule is attached to one specific amino acid.
Anticodon on tRNA binds to codon on mRNA (e.g. AAU anticodon to UUA codon.)
Hydrogen bonding between mRNA/tRNA bases.
Peptide bonds form between amino acids.
51
Suggest why common cold virus cannot infect cells via blood via cut.
Viruses only infect specific cells and only attach to specific receptors on host cells.
Receptors not present on blood/endothelial cells.
There is also the destruction of viruses by phagocytes.
52
Artificial active immunity from a vaccine.
Dead/attenuated organisms are injected into person.
Stimulation of specific primary immune response.
T helper cells are activated in response to macrophages acting as APCs (antigen-presenting cells). T helper cells release cytokines.
B cells are activated by cytokines and act as APCs.
T killer cells are activated by cytokines - infected cells act as APC which they destroy.
There is also the production of memory cells.
53
TB from tubercles
Reproduces rapidly and inhibits T cells.
2nd phase: the immunocompromised.
Further lung damage occurs.
Severe breathing problems occur e.g. cannot obtain enough oxygen.
Mycobacterium gets into blood/lymph.
There is a weakened/reduced immune response due to loss of T cells.
No T helper cells produce cytokines.
There are no T Killer cells, therefore infected cells will not be destroyed
There are no B cells so no antibody will be produced.
Secondary opportunistic infections therefore cause death.
54
Viral reproduction
Viral RNA is used.
Viral DNA is produced using viral RNAs a copy and using reverse transcriptase.
Viral DNA is integrated into host cell's DNA by action of integrase.
New viruses are produced - provirus formation occurs.p (viral RNA and proteins).
Infection of further T helper cells occurs and then are destroyed by T killer cells.
Immunity is lowered ( T helper cells work by producing cytokines to activate B cells or T killer cells.
Death is caused by opportunistic disease. TB. Kaposi's sarcoma.
55
TB antibiotics against dormant TB?
Bacteria need to be accessible to antibiotics.
The dormant bacteria are inside macrophages.
These bacteria have a waxy layer.
Bacteria static antibiotics affect dividing bacteria.
These bacteria have antibiotic resistance.
56
Describe how macrophages infect bacteria.
Phagocytosis/endocytosis/engulfing occurs.
There is the formation of pseudopodia/membrane extensions around bacteria binding to bacteria.
The bacteria goes inside a vesicle/phagosome.
57
Common cold RNA vs. retrovirus (HIV) RNA replication
No reverse transcriptase
No DNA formed
No provirus as formation of virus particles is immediate.
58
HIV RNA virus replication
Reverse transcriptase required
DNA is formed using RNA
Provirus/latency in virus formation
59
What is lysozyme and how does it work?
Lysozyme is an enzyme
Enzyme have a specific shape
Lysozyme acts on cell wall of bacteria
60
Interferon vs. Lysozyme
(Interferon)
Involved in viral infections
Produced by infected cells (is a cytokine)
Inhibits virus respiration
(Lysozyme)
Affects bacteria
Present IN phagocyte
Kills bacteria
61
Analysing insects on corpse
Forensic entomology
Example of insects: fly, beetle, and wasp
Types/ life cycle stages of insects are used
Decomposition
Different stages of decomposition
Production of gases, liquefaction of tissue, bloating, discolouration
Rate of succession/ insect development/ decomposition is influenced by external factors.
62
Flies and decomposition information is used to determine time of death
```
Different temperatures for flies
Have different enzymes
Temperature affects metabolism
Enzymes affect metabolism
Temperature affects enzymes
```
63
Anti-histamine cream better than drug
Only a local reaction produced.
Histamines are produced around bite area.
Cream has applied to actual site of production of histamine.
More rapid relief/effect.
64
HIV immunity by vaccine
Artificial active immunity
Vaccine contains authentic antigen/ glycoprotein
Stimulation of the specific immune response to the synthetic antigen
Process of producing effector B cells occurs: involvement of cytokines, T helper cells activate B cells.
Production of B memory cells.
2G12 antibodies are produced faster and in greater concentration on reinfection - secondary immune response.
65
Monoclonal easier than polyclonal antibodies - all clones from one unique parent cell
Specific pathogen can be identified
Specific antibody binds to specific antigen.
Specific antigen
Specific treatment can be given
Avoids unnecessary use of drugs more likely to be effective.
66
HIV infection does not always produce symptoms.
Provirus is formed.
There is latency.
The virus is dormant.
Test needed to detect symptomless HIV.
Only people who suspect they might have a contracted HIV would have a test.
Some people would not want to be tested - it is impossible to test everyone.
Symptoms are common to other diseases.
New cases arising/patients dying all the time.
New strains of virus arise.
67
Antibiotic agar plate test
Resistant if no clear zone -zone of inhibition - around discs
Clear zone indicates where the antibiotic kills bacteria/inhibits growth.
Diameter of clear zone indicates effectiveness.
68
DNA profiling - making copies
```
Polymerase chain reaction in PCR machine
Polymerase enzyme added
Need for primers and nucleotides
90-50-70'C
Cycle needs to be repeated
```
69
Forensic entomology
Body has been dead for a while
More than one species of insect present
Succession of insect species
Life cycle stages depend on environmental temperature
70
Corpse: body temp
A drop in body temperature is linked to rime after death (agar mortis)
Factors affecting temp.drop: environmental/ambient temp, body size,clothing
Useful because time of death can be calculated if ambient temp known
Only useful for short period of time following death e.g. 24 hours a day
71
Body decomposition sequence
Body decomposes in a specific sequence with time
Factors which affect: environmental,metal temp, wounds
Not useful if all the body has decomposed
72
Vaccination
Using virus as vaccine
Which is attenuated
Vaccine contains the antigen
Activation of specific B cell/T cell/ lymphocyte
Production of B/T memory cells
Body now able to produce specific antibody faster and at higher concentration on another exposure to virus.
73
Control group of patients - what is it and what is its purpose?
Given placebo
All other variables need to be controlled
So the only effect of the vaccine is studied
This ensures the experiment is valid
74
Start and stop/nonsense codon
Start codon needed to begin peptide synthesis
| Stop/nonsense codon needs to end peptide synthesis.
75
Glycogen granules: bacteria or viruses?
Bacteria
76
Nucleic acid - bacteria or viruses?
Both
77
Protein coat/capsid - viruses or bacteria?
Viruses
78
Protein synthesis
```
Sequence of bases forming genetic code
Determines the amino acid sequence
1 triplet code
Codes for an amino acid
DNA acts as a template
Transcription occurs
DNA unzips
mRNA is synthesised
Post transcriptional modification of mRNA occurs between transcription and translation e.g. removal of introns and splicing
mRNA moves from nucleus to cytoplasm
Translation occurs at ribosome ( with codon and anti-codon interaction).
tRNA carries an amino acid
Formation of peptide bonds between amino acids.
```
79
Transcription - how?
Sequence of bases on DNA determines sequence on mRNA.
Complementary base pairing occurs
Formation of bonds by condensation reaction
Phosphodiester bonds formed
RNA polymerase is used
80
Phagocytosis
Bacterium recognised as non-self and is labelled by B lymphocytes
Phagocytosis of the bacteria occurs.
A vacuole is formed.
81
Passive Immunity
Antibodies present at birth from mother via placenta , blood, milk
Passive immunity is short term as antibodies are excreted
Concentration falls if not infected
Concentration rises if present.
82
DNA structure
Double-stranded DNA because it is made of two strands
Strands joined by H bonds between bases
Polynucleotide (of many nucleotides)
Nucleotides linked by phosphodiester bonds.
83
Bacteria reproduction
By mitosis followed by cytokinesis (cell divides into two cells). Repeated many times.
84
TB characteristic symptoms
Tubercules
Bloody sputum
Body tissue wastage
85
Antigens
Bacteria are made of different chemicals/polymers which can act as antigens
Individual B lymphocytes recognise specific antigens
Antibodies are specific
B cells are activated by T cells
Mitosis in B cells occurs to form genetically identical plasma cells.
86
Primary to secondary structure to protein difference due to difference of mRNA exons
Primary structure different
| Secondary depends on primary and due to change in bonds (H/ionic/disulphides bonds) there is a different 3D shape.
87
Skin flora: preventing pathogenic bacteria infection
They provide inter specific competition for nutrients and for space.
They also secrete lysozyme
Affect pH so the pathogenic bacteria cannot survive there.
They also stimulate the skin immune system.
88
Active immunity
| Synthetic HIV antigens
This will be a method of artificial active immunity by using a vaccine containing the synthetic antigen
A specific immune response to the synthetic antigen will be stimulated, i.e effector B cells will be produced by clonal expansion of Bcells.
These will then produce B memory cells that will cause (2GI2) antibodies to be produced faster and in greater concentration on reinfection - secondary immune response.
89
Influenza may allow what other type of other diseases to develop?
Opportunistic infections
90
Vaccination
You may uses the virus as a vaccine which will contain an attenuated form of the virus that contains the virus' antigen.
The vaccine will stimulated the activation of specific B/T cells and causes the production of B/T memory cells: this means that the body is now able to produce specific antibodies faster and at higher concentration on exposure to the virus.
91
Resistance : what and how?
Some bacteria are resistant to antibiotics.
Resistance is genetic and can be passed on.
.e.g. MRSA has some resistant strains to particular antibiotics.
92
Body temperature factors for a corpse
```
BMI
Subcutaneous fat
SA
Ambient temp
Immersion in water
Age of person at death
Skin colour
Gender
Clothing
Blood loss
Humidity
Air movement
Core body temp at time of death
Physical damage
Immersion in water
External temp
Burning
Electrocution
Clothing
Wind/air movement
```
93
Standard deviation of time of death
SD shows spread and variability of data
In example
Most endings are within 1 x SC
.e.g approx 60% reading within 1 x SD
As length of time increases, SD increases
Meaning variability in temp as time increases
Time of death estimate can only be within a 4-7 hour period.
94
Transcription - describe
```
DNA strands separate/ unzip
One DNA stand used as template to form mRNA from free nucleotides
By complementary base pairings
H bonding occurs
RNA polymerase, DNA helicase action
```
95
Translation - describe
Specific amino acid attachment to tRNA.
Anticodon on tRNA bind to the codon/triplet on mRNA.
tRNA with alanine has CGA anticodon which binds to GCU on mRNA.
Two tRNA held in ribosome at any one time.
Peptide bonds form between adjacent amino acids.
By peptidyl transferase action
96
Stop codon in translation
Used to end the sequencing
Further attachment of tRNA
This enables the release of the polypeptide/ribosome.
97
Why does similarity in DNA indicate general similarity?
It indicates closeness of relationship
Because genes are sections of DNA
And genes are the codes for proteins.
98
How do antibodies work after a mutation in pathogen?
Some bacteria have changed antigens.
This is a primary infection
A mucus coat protects bacteria
Some bacteria are inside body cells
Antibodies are already present e.g. From passive immunity
Antibodies are protein in nature and are specific to each bacteria, with a specific antigen, so binding is able to take place.
99
Comparing antibiotics
Bacteria distributed evenly by lawn spreading
Multidiscs/wells in agar are used to apply different antibiotics at known positions
Antibiotic concentrations is controlled and constant
Sterile/antiseptic technique is used
Petri dishes are incubated at a sustainable temperature.
The effect is assessed: measure inhibition (clear) zones
Repeat experiment with same bacterium
Repeat experiment with different bacteria.
100
Bactericidal antibiotics
Cell wall weaker
Cell wall burst easy
During division
101
Antibiotic resistance
Antibiotic acts as a selective pressure
Some bacteria are resistant to antibiotics
Resistant bacteria survive and reproduce and pass on resistance gene
Antibiotic no longer effective
Also - some infections cannot be treated with antibiotics.
102
Virus protein synthesis: enzymes for which processes?
To synthesise viral RNA
For amino acids to bind to RNA
To synthesise protein capsid (translation)
103
Prokaryotes vs Eukaryotes
(Prokaryotes)
Plasmid
Small, circular loop of double-stranded DNA
(both)
Flagellum
Long strand-like structure, extending out of cell for locomotion.
(Eukaryotes)
Mitochondria
Enclosed by outer smooth membrane
Inner membrane folded producing crustal
104
Enzymes affecting molecules virus in membrane
Protease/lipase
Enzymes break bonds by hydrolysis
Lower activation energy
105
How do skin flora protect the body from infection?
Skin flora prevent growth of or kill pathogens.
Competition for space, nutrients, water minerals
Release of chemicals, toxins, antimicrobials, lipids, enzymes
106
Skin produces lipids, protect
They have antimicrobial properties that inhibit the growth of bacteria.
NOT
Alkalis which kill bacteria
Not enzymes which destroy viruses
Not water soluble and prevent from replicating
107
Skin contains a fibrous protein barrier
Keratin
108
Fibrous proteins
Little quaternary, tertiary structure
Mainly secondary structure
Made up of long, linear, straight, molecules and polypeptides
Cross-linking between one polypeptide chain and another
Repeating amino acid sequences
Insoluble
Tough, strong
109
Fibrous vs. Globular
```
(Fibrous)
Long, straight
Not folded
Insoluble
Involved in structures
Not catalysts,Not involved in metabolism
```
```
(Globular)
Spherical
Folded
Soluble
Not involved in structures
Involved in catalysis, metabolism
```
110
During the first few hours after the death of a mammal, the muscles undergo a characteristic contraction known as rigor mortis.
```
Factors immediately after death for progress of rigour mortis
Which one?
Degree of decomp of the muscle
Oxygen concentration of atomsphere
Presence of drugs in the body
Presence of egg laying insects
```
Presence of drugs in the body
NOT
Presence of egg laying insects
Degree of decomp of the muscle - not an immediate factor
Oxygen concentration of atoms - no more aerobic respiration
111
Antisense DNA strand and mRNA to primary structure of protein
DNA/mRNA contains the genetic code, triplet condones, base sequence coding for amino acid
DNA: the DNA strand is used in transcription to make mRNA.
mRNA: is a copy of the DNA
mRNA carries this information, code, out of the nucleus to the ribosomes.
Amino acids arranged in sequence.
112
Phagocytosis
Binding of pathogen, antigen, non-self to phagocytise cell
Pathogen is engulfed and is taken in by endocytosis into phagocytosis cell
Bacteria being inside a vacuole, phagosome
113
Non-specific response
The body reacts to a pathogen
The response is not dependent on the specific pathogen
Reaction: lysosomes, inflammation, phagocytosis, interferon production
114
Infection
Pathogen being inside tissues, cells
115
ADP to ATP
Phosphorylation
116
ATP to ADP
Hydrolysis
117
Structure of a mitochondrion
Two membranes shown
Inner membrane folded into cristae
Outer membrane and inner membrane , cristae
Matrix
Staked particle, ATPass on inner membrane
DNA circular
Ribosomes
118
Another organelle that synthesises ATP
Chloroplast
119
Gas exchange
TB infection, cough, blood
Photograph: tubercle: solid mass of dead tissue, macrophages, and bacteria
Alveoli sacs in healthy tissue
Alveoli have been destroyed and replaced by the tubercle
Tubercle and destroyed lung tissue has reduced the surface area of the luggage
Breathing problems due to gas exchange being reduced, less oxygen in blood
Coughing is due irritation to remove the dead tissue
Blood coughed up is due to damage of lung blood vessels
120
Natural selection increases in resistance
| TB for antibiotics
Bacteria have a mutation in DNA, gene
Presence,usage, of antibiotic acts as a selection pressure
The allele for resistance is passed on
Bacteria divide by asexual reproduction divide by binary fission, produce clones
Increasing the allele frequency
The more resistant bacteria there are, the more likely new strains will acquire the resistance gene.
121
Hospitals could prevent an increase in % of strains resistant to antibiotics
Codes of practice, conduct
Antibiotics should be given to patients
Educating patients about taking antibiotics, taking the full course of antibiotics
Hand washing, screening
122
Ambient and core temp of ta dead body used to determine time of death of a person
The temperature of the body, core, changes with time after death
Core temperature depends upon the ambient temperature
Other post death changes, muscle contraction, insect life cycles, decomposition, depend on ambient and body temperature
123
Clothing, position, air movement
| Dead body temp
Clothing
For the clothed body, the estimate was too short because the clothing would reduce heat loss, body would cool more slowly, temp would drop slower, clothing would insulate, trap heat
Position
For the body curled up, the estimate was too short
Because heat loss is reduced, body would cool more slowly, temp would drop slower as the exposed surface area was smaller
Air movement
For the moving air the estimate was too long , as moving air speeds up heat loss, body would cool faster, temp would drop faster.
124
```
Egg to larva to pupa to adult
Most effect on the rate of development of each stage of the life cycle of insects on this dead body.
Interspecific competition
Light
Predation by birds
Temperature
```
Temperature
125
Suggest how the pathologist might use the information in the table and the flow diagram to estimate the time of death of the young man.
Body has been dead for a while because more than one species of insect is present ( blowflies and beetles)
Succession of insect species has occurred
Life cycle times depend on environmental temperature
Blowfly cycle complete
126
DNA polymerase from human sources is not suitable is not suitable for use in a PCR machine
Do not work above 37'C
| Denaturation at temps in PCR
127
Species of plant cannot be identified from woody xylem material using PCR and DNA profiling
```
Made of dead material
No cytoplasm cell contents
No nuclei
No mitochondria
No DNA/nucleic acid present
```
128
Body temperature
Increase in body temp is linked to time after death, e.g algor mortis
Factors: ambient temp, body temp, body size, clothing
Useful because time of death can be calculated if ambient temp known
Only useful short period of time following death, e.g. 24 hours
129
State of decomposition
Body decomposes in a specific sequence with time
Factors affect decomposition: environmental temp, wounds
Not useful if all the body has decomposed.
