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Contemporary issues in biology 2Y > Forensics > Flashcards

Forensics Flashcards

1
Q

What is Locard’s principle?

A

Every contact leaves a trace (important to avoid cross-contamination.

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2
Q

What is trace evidence?

A

very small pieces of material which have been left and provide a link to an individual

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3
Q

Explain methods of recovering trace evidence

A

taping/ vacuuming/ swabbing/ hand picking/ extracting…

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4
Q

What are some sources of DNA found in crime scene ?

A

Glass/ fibres/ seamen/ saliva / blood/

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5
Q

Define forensic science

A

application of scientific methods and techniques to maters under investigation

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6
Q

What are factors to consider about blood when used as trace evidence?

A

blood stains - examining shapes and location can indicate events which occurred

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7
Q

How can you test for the presence of seamen?

A

miscopy of a the seamen sample which acid phosphatase has been added to , if sample turns purple seamen is present

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8
Q

What test can be used to test for saliva ?

A

starch/ iodine test ->if saliva is present saliva amylase will turn the black colour blue.

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9
Q

Which tests can be used to test for blood samples.

A

Leuchomalachite green test (LMG becomes reduced and when hydrogen peroxide is added the substance becomes green therefore indicating the presence of blood /// Kastle Meyer test uses the same principle and turns red

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10
Q

What are the two main principles in forensic science?

A

Locards exchange (every contact leaves a trace) and Physical fit (The evidence must be strong enough to create a link between the individual and the crime.

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11
Q

What are some effects from alcohol? When do they occur?

A

50mg/100ml = slurred speech/ co-ordination loss/// 100-150mg= nausea/// 150-200mg = nausea and non co-operative/// 200-300 = comba…. 400=death

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12
Q

What enzymes are involved in alcohol metabolism?

A

alcohol dehydrogenase (ADH)

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13
Q

What factors determine variance in alcohol metabolism in individuals?

A

liver size / body mass/ food intake

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14
Q

How are alcohol concentrations in the body determined ?

A

contact time with GI/ quantity of alcohol consumes/ concentration/ food intake/

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15
Q

How is alcohol cleared from the body

A

Ethanol is broken down by alcohol dehydrogenase into acetaldehyde which is then broken down in carbon dioxide and water

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16
Q

How is alcohol concentration measured within the body?

A

electrochemical fuelled breathalyser // infrared optical sensor breathalyser // dual sensor breathalyser / gas chromatography

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17
Q

What is the equation used to calculate alcohol elimination?

A

Cmax - (t X elimination rate )
maximum alcohol concentration -( time X elimination rate)

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18
Q

What is the elimination rate for individuals with :
average metabolism?
fast metabolism ?
slow metabolism?

A

average = 18 // slow = 9// fast =27

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19
Q

What does dosis factin venenum belive about poisonous?

A

Everything has the potential to be poisonous, it is the amount of it which determins if it is poisonous or not

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20
Q

What is meant by temporary class of drugs?

A

categorises illegal drugs which are chemically different to those found in another class

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21
Q

What is a forensic toxicologist?

A

investigates the presence or absence of compounds in relation to the law

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22
Q

What cases would be toxicologist be involved in?

A

Road traffic acts offences / drink driving/ drug driving / drug-facilitated sexual assault / sudden or suspious deaths

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23
Q

Be aware of overarching theme of the misuse of drug act.

A
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24
Q

What are some analytical techniques used to identify drugs

A
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25
What are some negative impacts of ecstacy?
effects temperature regulation // muscle cramping// blurred vision
26
What are the three main categories of drugs?
stimulates- stimulates brain / depressants- primary inhibits brain activity / hallucinogens- induces alterations in perception and mood
27
Give some examples of stimulates.
Amphetamines / cocaine
28
Give some examples of drugs in the category of depressants.
Alcohol/ Heroin / Benzodiazepines
29
Give examples of methods of analysing drugs
Presumptive tests / thin layer chromatography/ HPLC/ Mass spectrometry / Spectroscopy/ Immunaoassy
30
What is the aim of the majority of methods used to analyse drugs. (e.g. chromatography)
Separate components based on size and polarity
31
What is meant by synaptic plasticity?
Synapses change dose needed to create a response.
32
What are some negative effects of cocaine?
constricted blood vessels / nausea / raised blood vessels/ tremors / restlessness
33
How do you calculate probability of having a particular STR patten at one locus?
frequency of one allele X frequency of another allele // ***if heterozygote must multiply the answer by 2
34
What is an STR?
short tandem repeat - something which involves repeats between 1-6 base pairs
35
Why do forensics examine the STR patterns of several locus?
to ensure results are more reliable / allows a profile to be created despite certain areas of DNA being degraded
36
What is a partial profile and can it provide any useful information?
DNA analysis which does not cover all loci, can still create a comparison between samples and individuals but the results will not be as reliable (good for degraded DNA )
37
What is familial screening?
Screening and profiling the DNA of an entire family. Allows heritable diseases to be identified
38
Give some examples of uses for DNA profiling
identifying criminals / identifying illegal trade of wild animals i.e ivory / understand meat content of food
39
What are some issues with DNA evidence?
human error / technical failure / contamination / PCR stutter (polymerase slips
40
What are the 3 possible outcomes from DNA profiling?
exclusion = non-match/ inclusion = match// inconclusive
40
How are blood groups determined?
by the antigen present (e.g. group A has antigen A present)
41
What does it mean if an individual is a 'secretor'?
HAVE THE FUT2 GENE //The individual secretes fluids (can be saliva/ blood/sweat...) secretors have a higher concentration of A and B antigens -- more likely to be identified in crime scenes
42
Give some examples of good biological sources of DNA which may be found in a crime scene?
WBC - large nucleus// Sperm cells / Hair shafts with roots
43
Which sections of DNA are most useful for identification of individuals?
SNPs/ STRs are the main DNA variation individuals have
44
In scenarios where twins are involved in crime what additional factors can be considered rather than sections of DNA?
epigenetic markers= modifications of DNA due to environmental factors, alike diet/ smoking...
45
How do we get STRs?
During 'slippage' and miss realignment with the process of replication
46
Where do we inherit mitochondrial DNA from?
mother, maternal DNA
47
What are some methods of DNA profiling?
RFLP (restriction fragment length polymorphisms )= // PCR // mitochondrial DNA / Y-STR testing
48
What is RFLP DNA profiling?
measuring and detecting different lengths of DNA after restriction-enzyme digestion.
49
How can you calculate the probability of an individual having the named pattern of alleles?
frequency of allele 1 X frequency of allele 2 *if heterozygotic multiply this by 2
50
What are some issues with DNA evidence?
Degraded DNA/ Human error/ technical failure/ contamination / PCR stutters
51
What is the amylogenic locus, how does it help us determine the gender of an individual?
AMYLE X (X-chromosome) or AMYLE Y(y chromosome ) is present in every individual
52
What is partial screening?
DNA screening which identifies the suspect to be of close relative of samples you have
53
What are some additional uses of DNA profiling aside from criminal cases?
identification after natural disasters/ used in wildlife to find origins of animals, identify smuggling/ understand meat content / conservation
54
How can insects be used as evidence for PMI?
understand if the body has been moved (urban to rural) // circumstances around death (aquatic animals = interaction with water)
55
Why are insects good for forensic science?
Have regular and fast development (can identify how long an insect has been present for / life cycles are known) // they are small so can be analysed in labs easily // feeding - can indicate the presence of drugs // determine location of death
56
What properties of plants make them valuable to forensic science?
identify locations (plant traces) // pollen is a very good trace source // poisonous plants can be seen as a weapon // environmental context via pollen or plant fragments
57
What properties of plants make them valuable to forensic science?
estimate the time of death// through identifying pathogens or toxins// tracking body movement//
58
What are 4 main evidence used within crime scenes around death?
PHYSICL - Post-mortem changes / presence of insects // ENVIRONEMNTAL - indoor, outdoor, in water, burnt.../ HISTORICAL- victim habits, daily routines, relationships/ Additional evidence - watches stopped/ phone records...
59
What equation can be use to calculate hours since death.
(98.6 degrees F - internal body temperature ) divided by 1.5
60
Name some factors which affect rate of cooling of a body?
Size of body/ fat content// position of body (stretched or foetal )// blood loss// environemnt (dry/wet/cold/warm)//
61
What is livor mortis?
skin discolouration caused by pooling of blood(blood settles due to gravity , if face down blood migrates to body parts in contact with the floor.)
62
What is algor mortis?
cooling of the body
63
What is rigor mortis?
stiffening of skeletal muscles/ caused by a reduction of ATP within muscle cells
64
What is mummification?
body dries out, water is removed
65
What is apidocere?
hydrolysis of body fat resulting in bloating (water replaces body fat)
66
What is Accumulated Degrees Days?
the total temperature the body has been exposed to since death/ how many days it has taken the body to reach the level of decomposition identified by TBS(total body score)
67
What is the equation for ADD?
10^(0.002 x TBS X TBS + 1.81) +_388.16
68
What are the main stages of decomposition ?
1. FRESH (body cools, rigor mortis) // 2. BLOAT (discolouration, gas accumulates causing swelling) // 3. PUTREFACTION ( tissues liquify, skin blackens, body deflates.) // 4. ADVANCED DECAY( loss of skin and soft tissue)// 5. SKELETONISED (environmental and biological processes lead to complete decomposition of anything but skeleton.)
69
What test can be used to identify alcohol ?
EtG test, with a colour change from clear to pink if alcohol is present.
70
What is the test used for testing cannabis?
9 - carboxy- 11 nor- delta - 9 THC , turning a yellow precipitate
71
What is the test used to test for arsnic ?
DMA, solution becomes a chocolate brown precipitate when present
72
What test can be used to test for succinic acid ?
Succinic acid, turns whit perception.
73
What are the two poison which we tested for in the lab?
Succinic acid , Arsnic
74
Which stage of decomposition attracts the blowfly?
Fresh
75
Which drug affects the activity of glutamate?
D-lysergic acid diethylamide

Contemporary issues in biology 2Y (6 decks)

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