Lecture 3 - Forensic DNA Profiling Flashcards
Why is DNA useful?
- Most cells contain nuclear DNA
- Same no matter what cell type
- Does not change (much)
- Can be compared to DNA already in database
Forensic scientists only look at DNA we know is different between people
6 sources of DNA
- Blood
- Semen
- Saliva
- Skin cells
- Hair roots
- Foetal material
4 sources of DNA useful in body identification
- Finger/toe nails
- Body tissue
- Bone
- Teeth
3 types of DNA samples
- Case samples
- Reference samples (case specific)
- DNA profile databank
Types of DNA samples from reference samples
- Complainants
- Suspects
- Other people involved
Types of DNA samples in DNA profile databanks
- Criminal investigations (bodily samples) act 1995
- Convicted criminals (permanently held)
- Volunteers (can be removed on request)
- People police intend to charge (temporarily held)
What is YSTR crime sample databank?
Databank that only targets the Y chromosome (males)
What are the 3 data banks?
- DNA profile data bank
- Crime sample databank
- YSTR crime sample databank
What is the DNA laboratory process?
- Small sample
- Extract cellular material from the substrate, isolate DNA from cells
- Estimate how much DNA is present
- Amplify DNA by making copies of area of interest (PCR)
- Separate and detect the profiling results (electrophoresis)
What is DNA profile?
Set of profiling results obtained
What is locus?
A specific area or site on the DNA (plural: loci)
What is an allele?
An individual DNA profiling result
What are the conditions of the body that will determine DNA sample type?
- Fresh
- Decomposed
- Skeletal
- Burnt
- Complete or incomplete
Why is DNA not always the best technique?
- Slow (DNA profiling requires a specialist laboratory)
- Need to process reference DNA samples
When is DNA the only option?
- No teeth or dental records
- No hands or feet for comparison
- If really unknown, DNA profiling bank can help
- Coroner really wants to be certain about the identification