6A Forensics Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

how to determine T.O.D

A
  • body temp
  • extent of rigor mortis
  • level of decomposition
  • entomology
  • stages of succession of insects
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

after what period of time is body temp no longer useful?

A

24 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what conditions affect rate of cooling of body?

A
  • body size -> bigger bodies have SMALL s.a : vol = slower
  • body position -> bunched up = slower
  • clothing -> clothes = slower (traps heat)
  • air movement -> no air = slower (movement takes heat energy away)
  • humidity -> more = slower (like mummies in Egypt)
  • temp of surroundings -> higher = slower (mummies)
  • water = faster (takes heat energy away)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

rigor mortis

A

stiffening of muscles and joints after death

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

how does muscle size affect rigor mortis?

A

small muscles stiffen FIRST and unstuffed LAST

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

why does rigor mortis occur?

A
  • muscles run out of ATP -> actin and myosin (muscle fibres) stick together
  • muscles unstiffen when muscle fibres start to break down

no O₂ = anaerobic = makes lactic acid = lowers pH = DENATURES enzymes that make ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

if body is WARM and NOT STIFF how long ago since death?

A

no more than 3 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

if body is WARM and STIFF how long ago since death?

A

3-8 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

if body is COLD and STIFF how long ago since death?

A

8-36 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

if body is COLD and NOT STIFF how long ago since death?

A

> 36 hours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

autolysis

A

breakdown of body tissues using body’s own ENZYMES from dig system and lysosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what happens after autolysis?

A

bacteria from gut invade TISSUES and release MORE ENZYMES

-> usually in ANAEROBIC CONDITIONS so favours anaerobic bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what happens in first 36 hours of decomposition?

A

greenish colour in abdomen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what happens in 36-72 hours of decomposition?

A
  • greenish colour spreads to rest of body
  • abdomen darkens to reddish green
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what happens in after 72 hours of decomposition?

A
  • discolouration darkens to purple black
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what happens one week after decomposition?

A

gas/liquid blisters appear eg. H₂SO₄, CO₂

gases from respiring organisms that break it down eg. bacteria

17
Q

what happens more than one week after decomposition?

A

gas released and body DEFLATES

18
Q

how does heat affect autolysis?

A

autolysis …

increased by mild heat
decreased by intense heat

19
Q

how does humidity affect autolysis?

A

dry conditions = slow autolysis and can stop it in some conditions

vice versa

20
Q

forensic entomology

A

study of insects and their relation to a criminal investigation

21
Q

how can insects in dead body affect T.O.D?

A
  • age of maggots determined by LENGTH and area they are found in and using LIFE CYCLE
  • some maggots taken to lab -> grow them and note how long to pupate -> so deduce age
22
Q

how to identify body?

A
  • fingerprints
  • dental records
  • identity papers
  • GENETIC FINGERPRINT (DNA profile)
23
Q

what is purpose of electrophoresis?

A

separate DNA fragments to use for DNA fingerprinting

24
Q

describe gel electrophoresis (after PCR)

A
  1. DNA placed in well in gel and covered in buffer solution (conducts electricity)
  2. electrical current passed through gel -> DNA fragment is -vely charged = move towards anode at far end of gel
  3. short DNA fragments = move FASTER and travel FURTHER through gel -> so DNA fragments separated according to LENGTH
25
Q

what is polymerase chain reaction (PCR)?

A

technique used to create many copies of DNA segment

26
Q

describe PCR

(used to amplify DNA)

A

reaction mixture made …
- DNA sample
- free nucleotides
- primers
- DNA polymerase

  1. mixture heated to 95 °C -> breaks H-bonds between 2 strands of DNA
  2. mixture cooled to between 50 - 65 °C -> so primer can bind to strands
  3. mixture heated to 72 °C -> so DNA polymerase can work
  4. DNA polymerase lines up free DNA nucleotides alongside each template strand = complementary strands
  5. 2 new copies of fragment of DNA made and ONE CYCLE PCR COMPLETE
  6. cycle starts again -> all 4 strands used as templates
  7. each PCR DOUBLES amount of DNA
    eg. 1st cycle 2 x 2 = 4 DNA fragments
    2nd cycle 4 x 2 = 8 etc
27
Q

primers

A

short pieces of DNA that are COMPLEMENTARY to bases at START of fragment

28
Q

DNA polymerase

A

enzyme that CREATES new DNA strands

29
Q

satellites

A

repeated DNA seq within introns

a.k.a variable number tandem repeats

30
Q

DNA profile

A

fingerprint of organisms DNA

unique to you

used to identify people and determine genetic relationships