Unit 6

Question 1

Name the 3 ways to identify a body

Answer 1

• finger prints
• dna profilling
• dental records

Question 2

What are the 4 types of fingerprints?

Answer 2

Arch
Tented arch
Whorl
Loop

Question 3

How are fingerprints left?

Answer 3

Sweat and oil gather in the fingers and leave impressions when a surface is touched

Question 4

Describe an intron

Answer 4

a non-coding region

Question 5

Describe an exon

Answer 5

a coding region

Question 6

What does DNA profiling rely on?

Answer 6

The idea that everyone’s DNA (other than twins) is unique

Question 7

Within DNA, there are STR’s. What does that stand for and what are they?

Answer 7

Short Tandem Repeats are sequences of repeated bases

Question 8

Where do STR’s occur?

Answer 8

On the same loci on both chromosomes of a homologous pair

Question 9

Within a sequence of DNA, how many bases are there and how many times could this be repeated?

Answer 9

DNA could have 2-50 base pairs and could be repeated 5-100s of times

Question 10

How many STR’s are tested for and why?

Answer 10

10 STR’s are tested for as no 2 people are likely to have the same number of STR’s at each of the 10 loci

Question 11

What is a restriction endonuclease?

Answer 11

Enzymes used to cut the DNA in specific places and are used to cut out STR’s

Question 12

What is the Polymerase Chain Reaction?

Answer 12

A way that DNA can be copied to make a larger sample

Question 13

How are DNA primers used in PCR?

Answer 13

DNA primers are marked with fluorescent tags which attaches to the DNA to start the reaction

Question 14

What re the 3 stages of PCR and at what temperatures do they occur?

Answer 14

Denaturation= 95 degrees
Annealing= 68 degrees
Elongation= 72 degrees

Question 15

Describe the stages of PCR

Answer 15

1. The DNA is released using a detergent then added to a reaction tube
2. The sample is amplified the the DNA separates into 2 strands; this occurs at 95 degrees
3. Primers and fluorescent markers are attached to the start of the STR; this happens at 68 degrees
4. DNA polymerase is attached and nucleotides are added, extending the DNA from the primer
5. This is continued until the desired length

Question 16

Describe southern blotting

Answer 16

1. Fragments of double stranded DNA are loaded into wells in agarose gel in a tank
2. The DNA moves towards the positive electrode and separates into bands
3. DNA is transferred to a nylon membrane by solution drawn up through the gel. Double stranded DNA split and stick to the membrane
4. The membrane is put in a bag with a DNA probe. The DNA probe sticks to fragments with a complimentary sequence. The DNA probe will be radioactive or fluorescent

Question 17

Describe gel electrophoresis

Answer 17

1. Fragments of double stranded DNA, DNA primers and fluorescent tags are loaded into wells in agarose gel in a tank attached to a power supply
2. The DNA moves towards the positive electrode and separates into bands
3. The fluorescent tags will show up underneath a UV light

Question 18

Why do the bands of DNA travel different lengths?

Answer 18

The lighter fragments will move further than heavier fragments

Question 19

Where is body temperature taken?

Answer 19

In the rectum or through an insition made in the liver

Question 20

Why is body temperature useful within the first 24 hours?

Answer 20

Gives a more accurate representation of time of death

Question 21

Why might core body temperature be taken in the liver?

Answer 21

It is the organ that gives off most heat due to chemical reactions

Question 22

What factors may affect how fast a boy cools down?

Answer 22

• Body size and position
• Temperature of surrounding
• Clothing

Question 23

When and why does rigor mortis occur?

Answer 23

It occurs approximately 3 hours after death due to lack of oxygen

Question 24

Describe rigor mortis

Answer 24

1. After death, muscle cells become starved of oxygen and oxygen dependent reactions stop
2. Respiration becomes anaerobic and lactic acid is produced
3. The pH of cells fall, inhibiting enzymes and anaerobic respiration
4. The ATP needed for muscle contraction is no longer produced. Bonds between muscle proteins become fixed
5. Proteins can no longer move over one another, fixing the joints and muscles

Question 25

What is the first thing to occur after death?

Answer 25

Autolysis

Question 26

Describe the stages of decomposition

Answer 26

1. The first sign is putrefaction on the lower abdomen: this is due to sulfhaemoglobin in the blood
2. Discolouration will spread on the skin, turning reddish green, then purple
3. The body will smell and become bloated due to methane, ammonia and hydrogen sulffide
4. Gas and liquids drain away. Soft tissues shrink and the decay rate is reduced