Body identification
- Created by: Yzyl Quintana
- Created on: 06-02-17 17:05
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- Methods to identifying a body
- Fingerprinting
- Why?
- Sweat & oil secretions can leave impressions on surfaces we touch
- How?
- Fine aluminium
- Iron/Carbon powders that stick to the print (using superglue)
- Ninhydrin reacts with the amino acids in sweat, producing a purple-coloured fingerprint impression
- Magnets & iron flakes
- At least 16 points must be identical for fingerprints to match
- Why?
- Dental records
- Why?
- Tooth decays very slowly
- Can determine age by looking at the development of the teeth and roots
- Why?
- DNA profiling
- 1) Tissue sample obtained & DNA extracted
- 2) Amplifying the DNA
- PCR reaction
- DNA markers with fluorescent tags, DNA polymerase and nucleotides placed in sample
- Undergoes temperature changes in PCR machine
- Double-stranded DNA separated
- Optimises bindingof the primer to the target DNA sequence in the sample
- Polymerase attaches & replication occurs
- Restriction endonuclease
- Enzymes naturally found in bacteria
- Ezymescut Dan at specific base sequences
- Bacteria's own DNA not affected by their own restriction enzymes
- DNA sample cut into fragments only at site of STR
- PCR reaction
- 3) Separating the fragments
- Gel electrophoresis
- DNA placed on a gel of agarose
- Provides a stable medium where the fragments can move
- Then submerged in a buffer solution
- Connected to electrodes that produce PD across the gel
- DNA placed on a gel of agarose
- Gel electrophoresis
- 4) Visualising the fragments
- Southern blotting
- Transfers the fragments to nylon membrane
- Membrane place on gel
- Dry absorbent paper placed on top
- Draws the buffer solutions through the gel, carrying DNA fragments on to the membrane
- During this: DNA fragments maintain their position and are denatured into SINGLEstrands, exposing its base sequences
- Draws the buffer solutions through the gel, carrying DNA fragments on to the membrane
- Membrane incubated with labelled probe
- Radioactive probe
- Membrane is dried and placed next to an X-ray film
- Film blackens wherever probe has hybridised
- Fluorescent probe
- Position on membrane can be visualised under UV light
- Radioactive probe
- Southern blotting
- Fingerprinting
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