Forensic science Flashcards
list the 3 advantages of using DNA testing (than ABO blood group)
- very sensitive: can be used on invisible traces= solves many crimes
- High discrimination: prime evidence (ID ppl specifically except identical siblings)
- Can ID unknown suspects
What protocols are in place to minimise contamination
- use highly restricted access lab areas
- Staff elimination DNA database & regular visitors (IT staff)
- WA police elimination database
- use of human DNA-free consumables where possible
DNA profilingstages
- DNA extraction
- DNA quantitation: real-time PCR, only viewing human specific DNA not bacteria
- Amplification by multiplex PCR
- Analysis by capillary electrophoresis (rapid, accurate, sensitive)
difference between sequence polymorphism (SNP) & length polymorphism
SNP: single nucleotide mutation
LP: looks at short tandem repeats (STR) or microsatelite DNA
6 desirable features for forensic STR systems
- Hi heterozygosity: differentiate ppl
- Regular repeat unit: predicatable alleles
- distinguishable alleles: analyse tetra-nucleotide (4bp) repeats
- Robust amplification: inhibitors
- can be multiplexed: less DNA required, faster
- small product sizes: <500bp range): better for degraded DNA
what does it mean when a DNA can absolutely exclude a suspect but not their involvement
the DNA profile does not match the person but that result cannot exclude their involvement
what information can a forensic DNA profile give?
only the gender of the individual
What information can a forensic massive parallel sequencing give?
- ethnicity, racial background, country of birth or skin colour
- age of person
- predict the physical appearance (hair, colour, eye colour, height etc)
how can familial database searching be helpful in ID an unknown offender?
- use when there is no matching DNA profile on state or National database
- so possible that an offender’s close biological relative might be there: siblings = number of matching alleles overall OR raent/child = min of one shared allele at each locus
how can age be predicted from a DNA sample?
inc methylation = inc age
