The Case of the Druid Dracula: Clicker Case Version

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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.
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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 Mabels 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 BBCs Crimewatch December 2001
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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.

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CQ1 What is your blood type?

• A A
• B B
• C AB
• D O
• E Dont know

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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

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DNA in the Cell
chromosome
double stranded DNA molecule
individual nucleotides
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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
5CCCTAGGGTCTATAACGCCTAGTGTGTTGATTC
5 3GGGATCCCAGATATTGCGGATCACACAACTAAG 3
Y X
5CCCTAGGGTCTA---------GTGTGTTGATTC
5 3GGGATCCCAGAT---------CACACAACTAAG 3
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Gel Electrophoresis Sizing DNA Fragments
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CQ2 The DNA fragment indicated is approximately
____ base pairs in size.
A 300 B 350 C 580 D 600 E 700
bp?
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Why do the two DNA fragments indicated differ in
how bright they appear?
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DNA Structure
5' end
3' end
Two DNA chains

• Complementary

• Antiparallel

3' end
5' end
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CQ3 Below is one strand from part of the
amelogenin gene. What is the nucleotide sequence
of the other strand?
5-CCCTGGGCTCT-3
A 3' -ACTGTTAGATT-5' B 3' -GGGACCCGAGA-5'
C 5' -GGGACCCGAGA-3' D 3' -CCCTGGGCTCT-5'
E 5' -CCCTGGGCTCT-3'
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Copying DNA (Replication)
DNA strands are separated
- - - - - - - -
Each single strand is used as a template to make
a complementary strand
Two identical DNA molecules are produced
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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.

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Enzymes Perform Replication
Replication fork
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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.
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Amplifying DNA with PCR (Polymerase Chain
Reaction)
Target region
In 32 cycles at 100 efficiency, 1.07 billion
copies of targeted DNA region are created
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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.

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CQ6 Which of the strands of DNA could act as a
primer for the DNA sequence shown below?
5-CCCTGGGCTCTGTAAATGTTTCTAAGTG-3 3-GGGACCCGAGAC
ATTTACAAAGATTCAC-5
A 3' -ACTGTTAGA-5' B 3' -AAATTTGGC-5' C 3'
-ATGCTTTGA-5' D 5' -GGGACCCGA-3' E 5'
-CCCTGGGCT-3'
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Automated gels
110 bp
101 bp
MW
Amelog.
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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
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CQ8 Is this enough to convict a suspect?

• A Yes
• B No

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Additional Markers
Short Tandem Repeats (STRs)

• Chromosomes 11 of suspect 1

• Different people have different numbers of
  repeats on their chromosomes

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Positions of other STR regions
TPOX
CSF1PO
TH01
Each person is unique
AMEL
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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.

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CQ9 What is the chance that someone might have 5
and 7 repeats for the STR THO1 just by accident?

• A 1/200
• B 1/206
• C 1/600
• D 1/1200
• E 1/2600

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Hardmans 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 Hardmans 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.