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Forensic Examination
September 11, 2006
Serology:
Stains from the victim's clothing were prepared for DNA analysis. Several revealed poor quantities of intact DNA. However, there were 5 stains that were typable using the DQ alpha and Polymarker tests. A sample from the Victim (F) was included in each analysis for comparison.
DQ alpha Analysis | Polymarker Analysis
The DQ alpha test looks at a total of 8 alleles at the DQ alpha locus (1.1, 1.2, 1.3, 2, 3, 4.1, 4.2, 4.3). A sample originating from one person can be either homozygous (the same allele on each chromosome) or heterzygous (different alleles on each chromosome). A homozygous result still does not ensure a pure sample as it can originate from at least 2 people with the same homozygous genotype (e.g. a mixture of two people with the genotype 2, 2). However, the definite presence of 3 or more alleles indicates a mixture as the maximum number of alleles one person can donate is 2.
A |
|
B |
C |
D |
E |
F |
Sample |
Location |
Alleles Present |
Description |
A |
Shirt sleeve |
1.1, 1.3, 2, 3, possibly 1.2 |
Definite Mixture |
B |
Front of shirt |
1.1, 1.3, 3, possibly 1.2 |
Definite Mixture |
C |
Back of shirt |
1.1, 1.3, 3, possibly 1.2 |
Definite Mixture |
D |
Baseball bat, grip |
1.1, 4.1, possibly 1.2 |
Possible mixture |
E |
Baseball bat, end |
3 |
1+ donors with identical 3,3 genotype |
F |
Sample from Victim |
3 |
3,3 |
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Polymarker Analysis
The Polymarker test look at 5 more loci: LDLR (2 alleles A and B), GYPA (2 alleles A and B), HBGG (3 alleles A, B and C), D7S8 (2 alleles A and B ) and GC (3 alleles A, B and C). Again, a sample originating from one person can be either homozygous or heterzygous and a homozygous result still does not ensure a pure sample as it can originate from at least 2 people with the same homozygous genotype (e.g. a mixture of two people with the genotype A, A). However, the presence of 3 alleles indicates a mixture.
A |
|
B |
C |
D |
E |
F |
Sample |
Location |
LDLR |
GYPA |
HBGG |
D7S8 |
GC |
A |
Shirt sleeve |
A |
A, B |
A, B |
A, B |
B, C |
B |
Front of shirt |
A |
A, B |
A, B |
A |
C |
C |
Back of shirt |
A |
A, B |
A, B |
A |
C |
D |
Baseball bat, grip |
A |
A |
A |
A, B |
A, C |
E |
Baseball bat, end |
A |
A |
A |
A |
C |
F |
Sample from Victim |
A |
A |
A |
A |
C |
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