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 RepeatPolymorphism (Analysis)

First locus identified: D1S81990, Alec Jeffrey19 bp for each repeat containinghighly variable 1 bp in theHaeIII siteHundreds markers give sifficientpolymorphism

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 – DQ1

Forensics – DNA analysis

Sequence Polymorphism

Consideration of Markers

• RFLP• DQ1 • STR (VNTR)• SNP

• Restriction enzymes• Blot • PCR• DNA micro array

Better PolymorphismIncreased DensityLess Sample AmountsEasier TestMore 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 BC D E

“The bungledburglary” or“The burglarthat couldn’t”

The “missing person” case:

Using PCR based polymarkerloci GYPA, HBGG, D7S8, GCDQA1, STR TRIPLET.Gender identification locus:amelogenin

Suspect & roommate excludedfrom blood on carpet and shoes.Roommate excluded.Suspect pled to first degreemurder.

The gender IDmarker

The case of disappearing sperm:

DQ was the only locus validated forPCR 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 typingmarker concentration= one million / genome

RFLP results

5 and 6; 7 and 9 areindistinguishable

The first RFLP case (State v. Tommy Lee Andrews)

1353

Lane 3: Victim controlLane 5: Vaginal swabLane 13: Andrew