DNA Analysis
Bellringer
Take out your review sheet from
yesterday.
Objectives
 Introduction to the characteristics
of DNA and DNA analysis.
Quiz on Friday
 Study your review sheet
DNA
 DNA “fingerprinting” is a common way
to identify people by their unique
genetic code
 DNA “profiling” is a better way to refer
to the process; it has nothing to do with
fingers or fingerprints.
DNA
 Where can you find DNA?
 DNA is in every nucleated cell of the
human body and can be extracted from
blood, semen, urine, bone, hair follicles,
and saliva.
DNA
 What types of crimes does DNA
evidence help solve?
 DNA is currently being used to identify
the perpetrator in a crime, to identify
fathers in paternity cases, and to
identify unknown remains.
Aspects of DNA
 In the nucleus of cells are chromosomes that
are inherited from both parents.
 Chromosomes are long-chain DNA molecules
that are tightly bound in a specific structure.
 DNA (deoxyribonucleic acid) is the hereditary
material of most organisms. Held together by
hydrogen bonds
Chromosomes
Chromosomes
Fun Fact
 If all of the DNA in
your body was
stretched out and
put end to end, it
would reach to the
sun and back more
than 600 times!
DNA
 The human body has approximately 35,000
genes
 Genes are simply portions of the DNA that
code the information required to make
specific proteins.
 Proteins determine human traits and
functions.
Genes
 Each gene has a specific code for a
specific body function; they are the
fundamental unit of heredity,
determining traits from hair color, eye
color, and facial features to certain
diseases or disorders.
Human Genome Project
 Began in 1990
 Set out to identify all of the genes of
humans, and the order they are in.
 We did it.
DNA Structure
 The structure of DNA is important to its
function.
 An unusual property of DNA is its ability
to replicate itself.
 It is arranged in a right-handed double
helix pattern.
 Twisted ladder
DNA Structure
 The sides of the helix are the sugar and
phosphates groups (acidic properties)
 On the inside are the base pairs.
 Ladder rungs
 The average DNA molecule contains 100
million nucleotide groups.
DNA Structure
 The order of these pairs
is 99.9 percent the
same for everyone.
DNA
 Genes are different amounts of base pairs
(1,000 to several hundred thousand)
 A chromosome is a single DNA molecule
twisted and packed into the nucleus of the
cell.
 The sequence of the nucleotide bases is what
determines the proteins that will lead to
specific growth, function, and reproduction.
Twins
 Identical twins share 100 percent
identical DNA.
 Fraternal twins share only 50 percent of
their DNA, just like regular siblings.
 This makes for some twists in crimes!
How you get your DNA
Checkpoint
 What are chromosomes?
 How is DNA like a fingerprint?
Forensic Uses of DNA
 Read pages 340 to 345 in the textbook and answer
the following questions:
1. How and when was the first criminal case to use
DNA evidence?
2. What type of blood cell contains DNA?
3. How many nuclei are in a single drop of blood?
4. Name 4 uses of DNA profiling
5. What is used to release DNA from the chromosome?
6. What are the four main procedures involved in DNA
fingerprinting?
Answers
1. Blood samples were taken for DNA testing in 1986.
2. White blood cells contain DNA because they have a
nucleus.
3. A single drop of blood contains between 7,000 to
25,000 nuclei.
4. Clearing the wrongly accused, identifying victims,
establishing family relationships, and identify
suspects.
5. Enzymes are used to release DNA from the
chromosomes.
6. Isolation, Cutting, Sorting, and Analyzing.
Bellringer
 Where is DNA located in the body?
Objective
 Learn how forensic scientist extract
DNA from a chromosome
Answers
1. Blood samples were taken for DNA testing in 1986.
2. White blood cells contain DNA because they have a
nucleus.
3. A single drop of blood contains between 7,000 to
25,000 nuclei.
4. Clearing the wrongly accused, identifying victims,
establishing family relationships, and identify
suspects.
5. Enzymes are used to release DNA from the
chromosomes.
6. Isolation, Cutting, Sorting, and Analyzing.
DNA
 The base pairs of DNA
only have two
possibilities
1. Adenine –Thymine
2. Guanine-Cytosine
 Written as A,T,G, & C for
short.
Statistical Analysis in DNA Profiling
 The DNA molecule is hundreds of thousands of base
pairs long.
 Break the DNA molecule at certain points to form
fragments. Then compare the size and amount of
fragments.
 1 in 5 million chance of someone else sharing your
profile
RFLP Analysis
 R-Restriction enzymes are used to cut the
DNA into F-Fragments that are many different
L=Lengths and exhibit P-Polymorphism,
which means many shapes.
 The length of these fragments varies greatly
among individuals
RFLP Analysis
 A DNA sample is placed in a special tank that
has an electric charge going across it.
 An enzyme is added to the tank the cuts the
DNA at specific spots.
 The different lengths of DNA then move
across the tank at different speeds depending
on their length.
RFLP Analysis
Checkpoint
1. What are the two possible base pairs of DNA?
2. What does RFLP stand for?
Bellringer
 How does RFLP analysis work, and why
is it done?
Objectives
 Finish RFLP testing activity
 Know when to use each of the four main DNA analysis
techniques.
Movies
Simulation of RFLP –pg 346
 Use a meter stick to mark off every 2.5cm on
your strip of paper, and then draw a long line
all the way down the center.
 In every 2.5 cm box write four letters in any
order, and in any combination that you want
(A,T,G,C).
 After you filled in the top, fill in the bottom
with the complementary letter below.
Simulation of RFLP –pg 346
 Make cuts at the A-T boundary
 Then measure each of the fragments with a ruler;
record the length on the back of each strip
 Make the same chart as the in the TB and fill in the
first column with your data.
 Bring your data to me once you’re done.
Simulation of RFLP –pg 346
Length
1
2
3
4
5
6
7
8
9
1320cm
1
5
3
3
2
3
1
3
5
9-13cm
2
2
2
4
5
2
3
4
4
6-9cm
0
0
4
4
7
4
6
3
1
4-6cm
3
0
5
4
2
2
4
2
2
2-4cm
2
4
5
3
2
3
8
4
2
0-2cm
1
1
5
2
2
1
8
9
0
Simulation of RFLP
 A DNA sample
found at the scene
of the crime with
the following RFLP
data came back
from the
lab…whose is it?
Length
?
1320cm
4
9-13cm
4
6-9cm
2
4-6cm
3
2-4cm
6
0-2cm
10
Polymerase Chain Reaction
 PCR is a lab technique used to “copy
and paste” a very small DNA sample
 Need 50 percent less DNA than what is
required for a RFLP test.
PCR
 Forensic scientists cut the DNA sample long ways,
breaking the weak hydrogen bonds
 Since the base pairs only bond in specific pairs, single
bases are added and they automatically attach
themselves in the cut DNA sample in the correct order.
 This process is then repeated until there is enough DNA
to complete a RFLP test
PCR Example
DNA sample found at crime, but too small to test
ATGC ACGT TATT GCTA ACTG TCGA CGAG CAAT CGCA TGCT
TACG TGCA ATAA CGAT TGAC AGCT GCAC GTTA GCGT ACGA
TACG TGCA ATAA CGAT TGAC AGCT GCAC GTTA GCGT ACGA
ACTGCTACGATGCATGCATGCATCAGATCAGTCGATGCATGCAGCTAGCTGATGC
ATGCTGACTGATGCTAGCTAGCTGATCGTAGCTAGCTGACTGATCGTAGCTAGCT
ATGC
ACGT TATT GCTA ACTG TCGA CGAG CAAT CGCA TGCT
GACGATCGTAGCTAGCTCGACTGATCGTAGCTGACTGATCGTAGCTAGCTGACGA
TACG
TGCA ATAA CGAT TGAC AGCT GCAC GTTA GCGT ACGA
GACGTAGCTAGCTGATGCAGCTGATCGATCGTAGCTCGACGAGCATCGAGCATG
ATGC ACGT TATT
GCTA ACTG TCGA CGAG CAAT CGCA TGCT
ATGC ACGT TATT GCTA ACTG TCGA CGAG CAAT CGCA TGCT
TACG TGCA ATAA CGAT TGAC AGCT GCAC GTTA GCGT ACGA
PCR
 After one split they have 2 times the original DNA
 After two splits they have 4 times the original DNA
 After three splits they have 8 times the original DNA
 After ten splits they have 1024 times the original DNA
Checkpoint
 What is the point of PCR testing?
 How is PCR different RFLP?
Bellringer
Objectives
Updates
 Movies
 Entomology Tests
Short Tandem Repeats
 New technique that is becoming more
common than RFLP because it takes less time,
less of a sample size, and is more
exclusionary.
 STRs are locations on the chromosome that
repeats a specific sequence of two to ten
base pairs.
STR
 Thousands of STR sites have been
identified
 They are located on almost every
chromosome in the body
 Easily amplified using PCR
STR
 Forensic scientists scan 13 DNA regions that
vary from person to person
 They use the data to create a DNA profile of
that individual
 There is an extremely small chance that
another person has the same DNA profile for a
particular set of regions
STR
 STR analysis is now the primary method for
genetic profiling
 In 1992 the Innocence Project at the Cardozo
School of Law started using STR tests to free
wrongfully convicted people from jail.
 As of January 7th, 2014 312 have been exonerated
 As of May 29th , 2014 316 have been exonerated
Checkpoint
 Why is STP more widely used today than
RFLP?
Mitochondrial DNA
 Mitochondria is the powerhouse of the cell, providing 90
percent of the energy a human needs to function
 Each cell contains thousands of mitochondria, each
containing several loops of DNA with 15,000-17,00 base
pairs.
 Unlike nuclear DNA, which if found on the chromosomes,
mitochondrial DNA (mtDNA) is inherited only from the
mother.
MtDNA
 Usually no change in mtDNA from mother to offspring
 Individuals with the same maternal lineage are
indistinguishable if mtDNA is used for analysis
 You, your siblings, your Mom, your Mom’s siblings,
your Grandma, your Grandma’s siblings, your Great
Grandma, your Great Grandma siblings, and so on all
share the same mtDNA!
MtDNA
 Analysis techniques are more sensitive than other
profiling techniques, more costly, and takes more
time.
 Cases in which hairs, bones, or teeth are the only
evidence retrieved from a crime scene are particularly
well-suited to mtDNA analysis.
Checkpoint
 When is MtDNA most commonly used?
 How much does MtDNA change from mother to
child?
 When should you use RFLP, PCR, STR, and MtDNA
analysis?
Example
 A very small sample of DNA is found at the scene of a
murder. You want to know whose it is. What DNA
test(s) should you carry out to process the sample?
Fake DNA
 Is it possible to fake your DNA results?
 Dentist raped his patient when she was
sedated. He installed a drain in his body with
someone else’s blood. This way the DNA from
his blood test wouldn’t match the DNA
recovered from the woman.
Old Evidence
 On pages 362 read the story in the blue box, then on page
363 read the case study.
1. How are these two stories similar?
2. How does DNA analysis help solve crimes by using old
evidence?
3. Why is it important to build up data bases, and save
evidence even after crimes have been cold for years?
Simulation of RFLP –pg 346
 Use a meter stick to mark off every 2.5cm on
your strip of paper, and then draw a long line
all the way down the center.
 In every 2.5 cm box write four letters in any
order, and in any combination that you want
(A,T,G,C).
 After you filled in the top, fill in the bottom
with the complementary letter below.
Bellringer
 What does RFLP stand for?
Objectives
 Finish our simulated RFLP DNA test.
 Textbook questions
 Notes on other DNA analysis
Simulation of RFLP –pg 346
 Going left to right make a cut on the top
strand at every AT sequence
 Going right to left make a cut on the bottom
strand at every AT sequence
 Measure each of the fragments with your
meter stick and write the length on the back.
 Fill in the chart, and get data from at least 8
other pairs
Simulation of RFLP –pg 346
Length
1
2
3
4
5
6
7
1320cm
4
3
2
2
4
4
0
9-13cm
4
2
3
1
2
3
2
6-9cm
2
2
1
4
2
2
2
4-6cm
3
0
3
8
5
3
14
2-4cm
6
1
3
7
4
3
10
0-2cm
10
4
1
10
1
3
10
8
9
Simulation of RFLP
Length
 A DNA sample
found at the scene
of the crime with
the following RFLP
data came back
from the
lab…whose is it?
1320cm
9-13cm
6-9cm
4-6cm
2-4cm
0-2cm
?
Forensic Uses of DNA
 Read pages 340 to 345 in the textbook and answer
the following questions:
1. How and when was the first criminal case to use
DNA evidence?
2. What type of blood cell contains DNA?
3. How many nuclei are in a single drop of blood?
4. Name 4 uses of DNA profiling
5. What is used to release DNA from the chromosome?
6. What are the four main procedures involved in DNA
fingerprinting?
Bellringer
 What is a RFLP DNA test?
Objectives
 Learn about other DNA analysis
techniques besides RFLP
 Bring laptops tomorrow if you don’t
want to use the schools
Statistical Analysis in DNA Profiling
 The DNA molecule is hundreds of thousands of base
pairs long.
 If you look at only a fragment of the DNA, what are
the chances of someone else having the same size
fragment?
 1 in 5 million chance of someone else sharing your
profile
Polymerase Chain Reaction
 PCR is a lab technique used to “copy
and paste” a very small DNA sample
 Need 50 percent less DNA than what is
required for a RFLP test.
PCR
 Forensic scientists cut the DNA sample long ways,
breaking the weak hydrogen bonds
 Since the base pairs only bond in specific pairs, single
bases are added and they automatically attach
themselves in the cut DNA sample in the correct order.
 This process is then repeated until there is enough DNA
to complete a RFLP test
PCR Example
DNA sample found at crime, but too small to test
ATGC ACGT TATT GCTA ACTG TCGA CGAG CAAT CGCA TGCT
TACG TGCA ATAA CGAT TGAC AGCT GCAC GTTA GCGT ACGA
TACG TGCA ATAA CGAT TGAC AGCT GCAC GTTA GCGT ACGA
ACTGCTACGATGCATGCATGCATCAGATCAGTCGATGCATGCAGCTAGCTGATGC
ATGCTGACTGATGCTAGCTAGCTGATCGTAGCTAGCTGACTGATCGTAGCTAGCT
ATGC
ACGT TATT GCTA ACTG TCGA CGAG CAAT CGCA TGCT
GACGATCGTAGCTAGCTCGACTGATCGTAGCTGACTGATCGTAGCTAGCTGACGA
TACG
TGCA ATAA CGAT TGAC AGCT GCAC GTTA GCGT ACGA
GACGTAGCTAGCTGATGCAGCTGATCGATCGTAGCTCGACGAGCATCGAGCATG
ATGC ACGT TATT
GCTA ACTG TCGA CGAG CAAT CGCA TGCT
ATGC ACGT TATT GCTA ACTG TCGA CGAG CAAT CGCA TGCT
TACG TGCA ATAA CGAT TGAC AGCT GCAC GTTA GCGT ACGA
PCR
 After one split they have 2 times the original DNA
 After two splits they have 4 times the original DNA
 After three splits they have 8 times the original DNA
 After ten splits they have 1024 times the original DNA
Bellringer
 What is the purpose if PCR DNA
analysis?
Objectives
 Learn about STR, mtDNA, and fake DNA
samples.
 We’ll be working on the school laptops on
Monday, so if you remember bring yours in if
you can.
NEOTWY’s
 Who would like to share their NEOTWY for
this week?
 Please pass up your NEOTWY’s
Short Tandem Repeats
 New technique that is becoming more
common than RFLP because it takes less time,
less of a sample size, and is more
exclusionary.
 STRs are locations on the chromosome that
repeats a specific sequence of two to ten
base pairs.
STR
 Thousands of STR sites have been
identified
 They are located on almost every
chromosome in the body
 Easily amplified using PCR
STR
 Forensic scientists scan 13 DNA regions that
vary from person to person
 They use the data to create a DNA profile of
that individual
 There is an extremely small chance that
another person has the same DNA profile for a
particular set of regions
STR
 STR analysis is now the primary method for
genetic profiling
 In 1992 the Innocence Project at the Cardozo
School of Law started using STR tests to free
wrongfully convicted people from jail.
 As of January 7th, 2014 312 have been exonerated
Checkpoint
 How can PCR tests help forensic
scientists analyze DNA evidence?
 What is the most common method of
genetic profiling?
Mitochondrial DNA
 Mitochondria is the powerhouse of the cell, providing 90
percent of the energy a human needs to function
 Each cell contains thousands of mitochondria, each
containing several loops of DNA with 15,000-17,00 base
pairs.
 Unlike nuclear DNA, which if found on the chromosomes,
mitochondrial DNA (mtDNA) is inherited only from the
mother.
MtDNA
 Usually no change in mtDNA from mother to offspring
 Individuals with the same maternal lineage are
indistinguishable if mtDNA is used for analysis
 You, your siblings, your Mom, your Mom’s siblings,
your Grandma, your Grandma’s siblings, your Great
Grandma, your Great Grandma siblings, and so on all
share the same mtDNA!
MtDNA
 Analysis techniques are more sensitive than other
profiling techniques, more costly, and takes more
time.
 Cases in which hairs, bones, or teeth are the only
evidence retrieved from a crime scene are particularly
well-suited to mtDNA analysis.
Fake DNA
 Is it possible to fake your DNA results?
 Dentist raped his patient when she was
sedated. He installed a drain in his body with
someone else’s blood. This way the DNA from
his blood test wouldn’t match the DNA
recovered from the woman.
Fake DNA
 The Phantom of Heilbronn
 A string of killings between 1993 and 2009 all had the
same DNA evidence, but were in Austria, France and
Germany, and had no other connections.
 The cotton swabs the detectives used to collect DNA
samples already had DNA on them from someone in
the factory that made the cotton swabs.
Old Evidence
 On pages 362 read the story in the blue box, then on page
363 read the case study.
1. How are these two stories similar?
2. How does DNA analysis help solve crimes by using old
evidence?
3. Why is it important to build up data bases, and save
evidence even after crimes have been cold for years?
Bellringer
 What is the difference between RFLP,
PCR, and STR testing?
Objective
 Practice applying your knowledge of
DNA and DNA analysis while learning
about the history and issues of DNA
evidence.
Laptop Activity
 Grab a partner and a laptop
 Go to my page on the Windsor School website
 http://www.windsor-csd.org/MrVERSPOOR.aspx
 Click “Forensics”
 Download the PowerPoint labeled “Student Copy – DNA
Analysis”
 Follow the PowerPoint, and answer the questions.
DNA Timeline
 http://www.dnai.org/timeline/index.html
 Go through the timeline and answer the following
questions:
1. What did Friedrich Miescher do?
2. Who discovered the double helix pattern of DNA?
3. What did Craig Venter do?
DNA Fingerprinting
 http://www.pbs.org/wgbh/nova/education/body/creat
e-dna-fingerprint.html
 Follow the link above and click view.
 Preform the RFLP test.
 Record the exact steps needed to fully develop DNA
fingerprints
 Who was guilty?
The Innocence Project




http://www.innocenceproject.org/
Follow the link above, and answer the following questions:
What is “The Innocence Project”
What is a false confession, how often do they occur, and why
do they occur?
 What is “Forensic Science Misconduct”, and what are the two
most common types of it?
 Why is eyewitness evidence not as reliable as DNA evidence?
 How can bad lawyering lead to a false conviction?