DNA analysis
• DNA typing (genotyping) – History
– A marker is any polymorphic Mendelian
character that can be used to follow a
chromosomal segment through a pedigree.
• Phenotypical markers: E.g. blood groups
• Restriction Fragment Length Polymorphism
(RFLP) markers – The discovery of restriction
enzymes not only provided a way to
engineer the DNA, but for the first time,
provided a marker that encompassed entire
chromosome.
Forensics – DNA analysis
• RFLP
– History
– Southern analysis
– Fragment length analysis
– Frequency
– Pattern used to identify individuals
Minisatellite Variable Repeat
Polymorphism (Analysis)
First locus identified: D1S8
1990, Alec Jeffrey
19 bp for each repeat containing
highly variable 1 bp in the
HaeIII site
Hundreds markers give sifficient
polymorphism
Forensics – DNA analysis
• Polymerase Chain Reaction (PCR)
– Discovery
– Principles
– Application examples
• The case of the Russian Czar
• The case of English Royals
• Crime scene identification
1
2
2
4
3
8
4
16
5
32
6
64
7
128
8
256
9
512
10
1024
11
2048
12
4096
13
8192
14
16384
15
32768
16
65536
17
131072
18
262144
19
524288
20
1048576
21
2097152
22
4194304
23
8388608
24
16777216
25
33554432
26
67108864
27
1.34E+08
28
2.68E+08
29
5.37E+08
30
1.07E+09
Short Tandem
Repeats
Forensics – DNA analysis
• Single Nucleotide Polymorphism - SNP
• Sequence Polymorphism – DQa1
Sequence Polymorphism
Consideration of Markers
•
•
•
•
RFLP
DQa1
STR (VNTR)
SNP
•
•
•
•
Restriction enzymes
Blot
PCR
DNA micro array
Better Polymorphism
Increased Density
Less Sample Amounts
Easier Test
More Expensive
•Length
•Hybridization
•Length
•Hybridization
Finding Common Characteristics of
elements
---Can you find common characters in the following figures?
1. These are “jollos”.
2. These are “plotz”.
3. Which are jollos and which are plotz?
A
B
C
D
E
“The bungled
burglary” or
“The burglar
that couldn’t”
The “missing person” case:
Using PCR based polymarker
loci GYPA, HBGG, D7S8, GC
DQA1, STR TRIPLET.
Gender identification locus:
amelogenin
Suspect & roommate excluded
from blood on carpet and shoes.
Roommate excluded.
Suspect pled to first degree
murder.
The gender ID
marker
The case of disappearing sperm:
DQa was the only locus validated for
PCR testing in forensics at the time.
No conclusion can be drawn from the
test results
The OJ Simpson case
This was a few years ago.
Now SNP typing
marker concentration
= one million / genome
RFLP results
5 and 6; 7 and 9 are
indistinguishable
3
5
13
Lane 3: Victim control
Lane 5: Vaginal swab
Lane 13: Andrew
The first RFLP case (State v. Tommy Lee Andrews)