Unit 6 Flashcards
Name the 3 ways to identify a body
- finger prints
- dna profilling
- dental records
What are the 4 types of fingerprints?
Arch
Tented arch
Whorl
Loop
How are fingerprints left?
Sweat and oil gather in the fingers and leave impressions when a surface is touched
Describe an intron
a non-coding region
Describe an exon
a coding region
What does DNA profiling rely on?
The idea that everyone’s DNA (other than twins) is unique
Within DNA, there are STR’s. What does that stand for and what are they?
Short Tandem Repeats are sequences of repeated bases
Where do STR’s occur?
On the same loci on both chromosomes of a homologous pair
Within a sequence of DNA, how many bases are there and how many times could this be repeated?
DNA could have 2-50 base pairs and could be repeated 5-100s of times
How many STR’s are tested for and why?
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
What is a restriction endonuclease?
Enzymes used to cut the DNA in specific places and are used to cut out STR’s
What is the Polymerase Chain Reaction?
A way that DNA can be copied to make a larger sample
How are DNA primers used in PCR?
DNA primers are marked with fluorescent tags which attaches to the DNA to start the reaction
What re the 3 stages of PCR and at what temperatures do they occur?
Denaturation= 95 degrees Annealing= 68 degrees Elongation= 72 degrees
Describe the stages of PCR
- The DNA is released using a detergent then added to a reaction tube
- The sample is amplified the the DNA separates into 2 strands; this occurs at 95 degrees
- Primers and fluorescent markers are attached to the start of the STR; this happens at 68 degrees
- DNA polymerase is attached and nucleotides are added, extending the DNA from the primer
- This is continued until the desired length
Describe southern blotting
- Fragments of double stranded DNA are loaded into wells in agarose gel in a tank
- The DNA moves towards the positive electrode and separates into bands
- DNA is transferred to a nylon membrane by solution drawn up through the gel. Double stranded DNA split and stick to the membrane
- 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
Describe gel electrophoresis
- 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
- The DNA moves towards the positive electrode and separates into bands
- The fluorescent tags will show up underneath a UV light
Why do the bands of DNA travel different lengths?
The lighter fragments will move further than heavier fragments
Where is body temperature taken?
In the rectum or through an insition made in the liver
Why is body temperature useful within the first 24 hours?
Gives a more accurate representation of time of death
Why might core body temperature be taken in the liver?
It is the organ that gives off most heat due to chemical reactions
What factors may affect how fast a boy cools down?
- Body size and position
- Temperature of surrounding
- Clothing
When and why does rigor mortis occur?
It occurs approximately 3 hours after death due to lack of oxygen
Describe rigor mortis
- After death, muscle cells become starved of oxygen and oxygen dependent reactions stop
- Respiration becomes anaerobic and lactic acid is produced
- The pH of cells fall, inhibiting enzymes and anaerobic respiration
- The ATP needed for muscle contraction is no longer produced. Bonds between muscle proteins become fixed
- Proteins can no longer move over one another, fixing the joints and muscles
What is the first thing to occur after death?
Autolysis
Describe the stages of decomposition
- The first sign is putrefaction on the lower abdomen: this is due to sulfhaemoglobin in the blood
- Discolouration will spread on the skin, turning reddish green, then purple
- The body will smell and become bloated due to methane, ammonia and hydrogen sulffide
- Gas and liquids drain away. Soft tissues shrink and the decay rate is reduced
