forensics lecture 4- DNA profiling 1 Flashcards
what is blood grouping?
-Still used in many countries
-Historical cases
-Large samples eliminated by quick inexpensive screening
-Discovery of more systems inherited independently of each other and ABO
what are the problems with blood grouping?
-Protein variants – not just blood cell related proteins!
-Quantity of blood may be limited
-Increase typing systems - decrease the number of people sharing the combination
what are biological markers?
ABO- AChE (Acetylcholine Esterase)
Rhesus- ACP (Acid Phosphatase)
MNS- Haemoglobin
Kell- PGM (Phosphoglucomutase)
Duffy- G-6-PD Glucose-6-phosphate dehydrogenase
when did DNA profiling begin?
1984 – (Sir) Alex Jeffreys
Discovered by chance
First Use – Conviction of Colin Pitchfork
what are secretors?
-75 - 85% of population
-Other body fluids have similar profile to serum.
-Higher concentration of A and B antigens
What are identical twins?
Have the same DNA
Rosslyn Chapel Rape
Developing technologies - methylation
Methodology - RFLP v PCR of STRs…
RFLP (Restriction Fragment length polymorphism) Analysis
Variable number tandem repeats
Large amounts of DNA required
Requires undegraded material (warm moist conditions increase degradation)
PCR (Polymerase Chain reaction) of STRs ( Short tandem repeats)
Less DNA required
Can be partially degraded
what is mitochondrial DNA?
-1 mitochondrion has 5-10 identical circular molecules of DNA
-Each 16569 base pairs – 37 genes
-Useful in mass disasters to link family members.
what are the odds ratios of each blood group?
Odds ratio of each blood group (UK)
O+ 1/3 O- 1/15 A+ 1/3 A- 1/16 B+ 1/12 B- 1/67 AB+ 1/29 AB- 1/167
what are good and bad sources of DNA?
good = blood, sperm, ovum, hair
bad = skin cells, faeces, hair shaft, urine
