The Case of the Druid Dracula:
Clicker Case Version
by
Norris Armstrong, Terry Platt, and Peggy Brickman
Adapted from Brickman (2004). The Case of the Druid Dracula. National Center for Case Study Teaching in
Science, University at Buffalo, State University of New York.
1
The Crime
In a quiet corner of Wales in the village of
Llanfairpwll, 90-year-old Mabel Leyshorn was
murdered. Her murder had been not only
brutal (her heart had been hacked out), but
also creepy. It appeared as if the Mabel’s
blood had been collected in a small kitchen
saucepan and tasted. The murder showed
other signs of the occult: a candlestick and a
pair of crossed pokers had been arranged
near the body.
- from BBC’s Crimewatch December 2001
2
The Crime Scene
Further investigation indicated that this was
no supernatural villain at work: the murderer
had worn tennis shoes which had left
distinctive footprints under the glass door that
had been shattered by a piece of broken
garden slate. Moreover, the windowsill had
bloodstains on it; with any luck, the evidence
recovery unit hoped to use it to help
determine who had committed the crime.
3
CQ1: What is your blood type?
A:
B:
C:
D:
E:
A
B
AB
O
Don’t know
4
Evidence in the Courtroom
• Blood was previously used for blood typing
• Now used as source of DNA
Sources of DNA?
Uses for DNA fingerprinting
• Primarily rape cases
• Paternity testing
• Historical/missing persons investigations
• Military “dog tag”
• Convicted felon databases
5
chromosome
DNA in the Cell
double stranded
DNA molecule
Target Gene
individual
nucleotides
6
Example: Amelogenin Gene
• Tooth enamel development
• Copies on X and Y chromosome
• X copy is different from Y copy
--- indicates missing bases
X copy is shorter than Y copy
5’CCCTAGGGTCTATAACGCCTAGTGTGTTGATTC 5’
Y:
3’GGGATCCCAGATATTGCGGATCACACAACTAAG 3’
5’
GTGTGTTGATTC 3’
X: 5’CCCTAGGGTCTA---------GTGTGTTGATTC
3’GGGATCCCAGAT---------CACACAACTAAG
3’
CACACAACTAAG 5’
7
Gel Electrophoresis: Sizing DNA
Fragments
(-) Negative electrode
bp?
bp?
(+) Positive electrode
8
CQ2: The DNA fragment indicated is
approximately ____ base pairs in size.
A:
B:
C:
D:
E:
300
350
580
600
700
bp?
9
Why do the two DNA
fragments indicated
differ in how bright
they appear?
10
DNA Structure
5′ end
3′ end
Two DNA chains
•Complementary
•Antiparallel
3′ end
5′ end
11
CQ3: Below is one strand from part of the
amelogenin gene. What is the nucleotide
sequence of the other strand?
5’-CCCTGGGCTCT-3’
A:
B:
C:
D:
E:
3′ -ACTGTTAGATT-5′
3′ -GGGACCCGAGA-5′
5′ -GGGACCCGAGA-3′
3′ -CCCTGGGCTCT-5′
5′ -CCCTGGGCTCT-3′
12
Copying DNA (Replication)
A- T
T-A
C- G
G- C
G- C
A- T
C-G
T-A
A -T
T -A
C -G
G -C
G -C
A -T
C -G
T -A
A- T
T- A
C- G
G- C
G- C
A- T
C- G
T- A
DNA strands are separated
Each single strand is used
as a template to make a
complementary strand
Two identical DNA
molecules are produced
13
Enzymes Perform Replication
• Helicases unwind DNA double helix.
• Single Stranded Binding Proteins hold
separated DNA strands apart.
• Primase makes a starting point (primer).
• DNA polymerase connects new
complementary bases.
• Ligase attaches pieces together.
14
Enzymes Perform Replication
Replication fork
15
CQ4: How would DNA replication be
affected if ligase were not available?
A: The template strands would not be able to
separate.
B: Replication would result in many small segments
of DNA instead of a complete molecule.
C: Complementary RNA would be produced but not
complementary DNA.
D: The DNA strands would separate but replication
would not be able to start.
E: The DNA strands produced by replication would
not be complementary to the template strands.
16
Amplifying DNA with PCR (Polymerase Chain Reaction)
Target region
Thermal cycle
In 32 cycles at 100% efficiency, 1.07 billion
copies of targeted DNA region are created
17
CQ5: You need many copies of the amelogenin
gene, which you will make using Polymerase
Chain Reaction (PCR). You will need to follow the
steps of replication. Which of the following would
allow you to begin?
A: Add short stretches of single stranded DNA
complementary to the sequence at either end of
the gene.
B: Add DNA polymerase enzyme.
C: Break the covalent bonds that hold the double
helix together.
D: Break the hydrogen bonds that hold the double
helix together.
18
CQ6: Which of the strands of DNA could
act as a primer for the DNA sequence
shown below?
5’-CCCTGGGCTCTGTAAATGTTTCTAAGTG-3’
3’-GGGACCCGAGACATTTACAAAGATTCAC-5’
A: 3′ -ACTGTTAGA-5′
B: 3′ -AAATTTGGC-5′
C: 3′ -ATGCTTTGA-5′
D: 5′ -GGGACCCGA-3′
E: 5′ -CCCTGGGCT-3′
19
Automated gels
110 bp
101 bp
MW Amelog.
20
CQ7: The blood left at the crime scene was from
a male. Which of the following DNA profiles
could have come from the suspect?
A:
B:
21
CQ8: Is this enough to convict a suspect?
A: Yes
B: No
22
Additional Markers
Short Tandem Repeats (STRs)
•Chromosomes 11 of suspect 1:
---TCAT-----TCAT---
•Same pair in suspect 2:
•Different people have different numbers of
repeats on their chromosomes
23
Positions of
other STR
regions
TPOX
CSF1PO
TH01
Each person
is unique
AMEL
24
Druid Dracula: DNA testing
• With kits just add DNA sample with primers
for amelogenin (XY) different STR regions.
• Amplify and electrophores.
• Allele ladder shows all varieties in population.
25
26
CQ9: What is the chance that someone
might have 5 and 7 repeats for the STR
THO1 just by accident?
STR THO1
frequencies
allele
5
1/200
6
1/4
7
1/6
8
1/7
9
1/6
9.3
1/3
10
1/100
A: 1/200
B: 1/206
C: 1/600
D: 1/1200
E: 1/2600
27
Hardman’s Arrest
• Standard police work identified Matthew Hardman
as a suspect. Preliminary DNA testing provided
enough evidence to arrest Hardman on suspicion of
murder.
• During the arrest, a knife was found in his coat
pocket. Subsequent DNA testing revealed two
sources of DNA on the knife, one from Hardman and
one matching the victim. The possibility of a random
match was one in 73 million.
• A search of Hardman’s dwelling produced
magazines and evidence of accessing internet sites
featuring how to become a vampire.
• Matthew Hardman was found guilty of murder on
August 2, 2002, and sentenced to life imprisonment.
28