Biology-Topic 6

Question 1

5 observations to estimate time of death

Answer 1

1) Body Temp (Algor Mortis)
2) Degree of Muscle Contraction (Rigor Mortis)
3) Forensic Entomology
4) Extent of Decomposition
5) Stage of Succession

Question 2

What is the cooling rate of a dead body?

Answer 2

1.5-2 degrees Celcius an hour

Question 3

Conditions that effect rate of cooling

Answer 3

Related to body- body weight, body position

External factors- clothing, air temp

Question 4

Time stamps for Rigor Mortis

Answer 4

4-6 hrs, beginning with smallest muscles first

12-18 hours after TOD for all muscles

Question 5

Why does Rigor Mortis occur?

Answer 5

Anaerobic respiration, lack of ATP for actin and myosin to move and so muscles remain contracted

Question 6

How can forensic entomology be used to estimate TOD?

Answer 6

Scientists have recorded the life cycle of insects for example flies. This can be used to estimate TOD by observing at what stage the flies are in the cycle which are found on the body.

Question 7

Time stamps for forensic entomology

Answer 7

Blowfly eggs take 24 hrs to hatch

Question 8

Factors affecting reliability of forensic entomology.

Answer 8

drugs, humidity, oxygen and temp (all can effect the metabolic rate, which effects the speed of the cycle)

Question 9

Features of decomposition at hours- days after TOD

Answer 9

cells broken down by own enzymes and bacteria.

Body turns a greenish colour

Question 10

Features of decomposition at days-weeks after TOD

Answer 10

microorganisms decompose tissue and organs.
Bloating of the body due to methane being produced,
skins blisters and falls off

Question 11

Features of decomposition weeks after TOD

Answer 11

Tissues begin to liquefy and seep out

Question 12

Features of decomposition months to years after TOD

Answer 12

Skeleton remains

Question 13

Factors affecting rate of decomposition

Answer 13

temperature, oxygen availability

Question 14

Name the stages of succession in decomposition

Answer 14

Autolysis, bacteria breakdown, larvae, beetles, only beetles, no tissue remains

Question 15

How is a PCR (polymerase chain reaction )carried out

Answer 15

Test tube with DNA, DNA polymerase, primers and free nucleotides.

1) Heated to break H bonds (90)
2) Cooled to bond with primers (50)
3) Heated for (non-human) polymerase to work (70)
4) Repeated to make more copies

Question 16

How is a DNA profile created?

Answer 16

Gel electrophoresis using a fluorescent tag or radioactive tag

1) placed in wells
2) +ve charge on the other end
3) Different lengths (of STRs) move different distances
4) Use UV light/ fluorescent tag to locate and compare

Question 17

How can DNA profiles be analysed

Answer 17

Analyse the width of bands, their location and the number of bands

Question 18

Adv of high temp for larvae in a dead organism

Answer 18

Decomposition and breakdown works faster.
Enzymes in the species work faster
Nutrients released faster.
High temp denatures/ kills other enzymes/ organisms

Question 19

Uses of DNA profiling

Answer 19

Identify suspect at crime scene
Prevent inbreeding
Paternity test