Name ______________________________________________ Period ____________ Date ________________________
Chapter 5: DNA Fingerprinting
Case Study -- O.J. Simpson A Mountain of Evidence
On June 12, 1994, police arrived at the home of Nicole Simpson only to view a horrific
scene. The bodies of O.J. Simpson’s estranged wife and her friend Ron Goldman were found
on the path leading to the front door of Nicole’s home. Both bodies were covered in blood
and had suffered deep knife wounds. Nicole’s head was nearly severed from her
body. This was not a well-planned murder. A trail of blood led away from the murder
scene. Blood was found in O.J. Simpson’s Bronco. Blood drops were on O.J.’s driveway and
in the foyer of his home. A blood-soaked sock was located in O.J. Simpson’s bedroom, and a
bloodstained glove rested outside his residence.
As DNA was extracted and profiled from each bloodstained article, a picture emerged that
seemed to irrefutably link Simpson to the murders. A trail of DNA leaving the crime scene
was consistent with O.J’s profile, as was the DNA found entering Simpson’s
home. Simpson’s DNA profile was found in the Bronco along with that of both victims. The
glove contained the DNA profiles of Nicole and Ron, and the sock had Nicole’s DNA
profile. At trial, the defense team valiantly fought back. Miscues in evidence collection
were craftily exploited. The defense strategy was to paint a picture of, not only an
incompetent investigation, but one that tinged with dishonest police planting
evidence. The strategy worked. O.J Simpson was acquitted of murder.
Introduction

No two people on Earth have the ___________________ DNA
o Except for __________________________ twins

DNA __________________________ has allowed criminal cases to be solved that were once
not possible to conclude

Since ________________, DNA evidence has been used to
o __________________________ crimes
o Establish __________________________
o Link a _______________________ to a crime
o __________________________ a suspect
o __________________________ victims of war/large-scale disaster

DNA evidence is __________________________ evidence because it can track back to
_________________ person

Can also be _______________________ evidence when a small amount is left behind
1
The Function & Structure of DNA

DNA contains the __________________________ material that holds the information to
produce proteins and __________________________ itself

DNA is stored in animal cells into a structure called a __________________________

DNA is made up of ___________________ strands tightly coiled called a
__________________________ __________________________

The backbone of DNA is alternating __________________________ (deoxyribose)
and __________________________

Made up of _____________________ bases
o _____________________________ to _____________________________
o _____________________________ to _____________________________

Every organism has a _____________________________ number of chromosomes
o Humans have ___________ pairs
o Dogs have ___________ pairs

Nuclear DNA
o Double ______________________ shape
o Inherited from _____________________ parents
o ____________________ of genetic information from
each parent
o DNA from _________________ cell from mom
o DNA from _____________________ cell from dad

mtDNA
o Found only in _______________________________ organelles
o Animal cells contain _________________________ mitochondria
o ______________________ shaped chromosome
o Inherited ONLY from _____________________________
o Passed to offspring in _____________________________ from _______________________ cell
2
Genes & Alleles

Genes
o DNA sequences with instructions for ________________________
o Ex: blood type

Allele
o Alternative ___________________ of a gene
o Ex: if the gene is eye color, the alleles would be brown and blue

Genome
o Complete ________________ of DNA in a cell
o _____________________________ and _____________________________

Exons
o DNA _____________________________ to make proteins and other molecules
o _____________________ the nucleus to make proteins (expressed)
o Less than _______________ of your genome

Introns
o _____________________________ regions of DNA
o Stay __________ the nucleus and are never coded
o Some functions for gene _______________________ and gene __________________________
o Remainder of introns has an _____________________________ function
3
DNA Identification

Most of human genome is the _____________________________

The areas of _____________________________ are in the ____________________ or the non-coding
regions of DNA
o _____________________________ base sequences
o Individuals have ________________________ patterns or repeat sequences


Different __________________________ and ________________________ of the bases

Called _____________________________
DNA Fingerprinting or DNA Profiling
o Takes the pattern of bands on _____________________ film
o Polymorphisms produce unique ______________________ patterns
o Forensic scientists focus on __________________ sections
STR – ____________________ ________________________ _________________________

Short sequence of DNA - between _______________ bases in length

Found in great _____________________________ in the human genome

Becoming a _____________________________ method of analysis
o More ________________________
o Small & partially degraded DNA samples can be _____________________________

_____________________________ of different types in human genome
DNA Fingerprinting

DNA can be extracted from ____________________ samples of ___________________________
evidence
o _____________________ – envelope, toothbrush, bite wound
o Hair _______________________
o _____________________
o ______________________ fluid
o _________________ cells
4

DNA _____________________________ developed when several different
STRs are examined

_________________________ matching
o When _______________________ samples have the same band pattern from the
same person
o Crime-scene evidence _____________________________

When DNA is mixed with special _____________________________ that cut DNA in specific
places, it will form different _______________________ DNA _____________________________

Using a technology called ____________________ _____________________________, these DNA
fragments can be _____________________________ within a gel

The results will form __________________ _____________________________ (or fingerprint) in
the gel specific to that individual

Relatives may _______________________ some bands and this is how this technology can
be used to identify _____________________________ and _____________________________
DNA Fingerprinting Steps
1. Extraction
o Cells _____________________________ from tissue
o DNA is __________________________ from the __________________________ of the cells
collected
2. Restriction Enzymes
o DNA is cut into fragments using biological _____________________________ known
as _____________________________ _____________________________
o These molecules _____________________________ specific sequences in the DNA
sample and cut in those _____________________________ locations

Ex: Hind III recognizes the AACGTT base sequence and cuts between
the two AA bases
o These sequences of tandem repeats are known as ____________________
sequences (Variable Number Tandem Repeats)
o Shorter sequences about 2-5 bases in length are known as _____________
sequences (Short Tandem Repeats)
5
3. Amplification
o Small samples of DNA evidence can be _____________________________ or copied in
a process called the _____________________________ _____________________
_____________________________ (PCR)
o _____________________________ – simultaneously extracting DNA and amplifying
4. Electrophoresis
o DNA is loaded into wells of an ______________________ gel
o Separate molecules within an _____________________________ field
o Negatively charged DNA fragments move to _____________________________ end of
the gel
o The process will separate the fragments of DNA by their _______________________

Smaller fragments of DNA will travel _____________________________ and
_____________________________ down the gel
DNA & Probes

If there are too many DNA restriction fragments, scientists use _______________________
to identify specific DNA sequences

Helps to make any DNA on the gel _____________________________

Made of _____________________________ DNA that is complementary to a fragment

For example, a probe AAGCTTA will find a _________________________ fragment and
attach

If probe is _____________________________, then you use a _____________ light to see the
probes

If probe is _____________________________, then you use ________________ film to see the
probes
o Called _____________________________
6
Population Genetics & DNA Databases

Study of _____________________________ in genes among a group of individuals

Proportion of people in a population with a particular characteristic is determined
by the proportion of the _______________________ for these traits in a population

Example:
o ____________________ population - blue eyes rare, few people have allele that
codes for blue eyes
o Northern _____________________________ - blue eyes common, more people have
allele that codes for blue eyes
o Europe/Great Britain/US - _______________ have type O Blood
o South America - almost _________________ type O blood
Collection & Preservation of DNA Evidence


Extremely small samples can become contaminated
o Sneezing
o Coughs
o Evidence collector touches own mouth or nose
To avoid contamination
o Wear disposable gloves and change often
o Use disposable instruments for handling each sample
o Avoid touching area where DNA may exist
o Avoid talking, sneezing, coughing over evidence
o Avoid touching face, nose, mouth when collecting and packaging
o Air-dry evidence thoroughly before packaging
o Place evidence in new paper bags/envelopes
o If wet evidence cannot be dried, may be frozen to preserve
o Keep evidence cool and dry during transportation and storage
o Mold can damage DNA
o Avoid plastic bags for DNA evidence
o Direct sunlight and warm conditions can harm DNA
Analysis of DNA Fingerprints
Which man is the father?
 Can either man be excluded as the father?

Which man may be the father of the child?

Is this DNA profile sufficient to establish
paternity?
7
Paternity

Child inherits ________________ gene from each parent

If two genes from parents are _____________________________, then _________________ bands
appear in child’s DNA fingerprint

If two genes are _____________________________, only _________________ band appears

The more ___________________ used in DNA fingerprint, the greater the ___________________
of the DNA fingerprint

Most criminal cases use ________________ probes

Analyze both _____________________________ and _____________________ of the bands

All bands have to match _____________________________
Analysis of DNA Fingerprints

Some countries have _____________________________ of DNA profiles

US has ________________________
o Combined DNA Index System
o Electronic _____________________________ of DNA profiles
o Every state maintains a DNA index of individuals convicted of _________________,
_____________________, child ________________________

Probability of identity is a measure of the _____________________________ that two
individuals selected at random will have an identical STR type

STR’s occur ______________________________, probability of having a particular
combination of STR types is determined by the product of their ________________________
in a population
8
The Break-in…
One afternoon, a break-in occurred at a high school, and several computers were stolen. At
the time of the break-in, the building was empty. A motion detector tripped by movement
in one of the hallways alerted the police. When the police arrived to investigate, they found
that one of the doors leading into the school had been propped open with paper wedged
into the door-jamb. The door appeared to be locked, but it could easily be pushed
open. Near the door, police found a cold soft drink can. Because of the cool temperature of
the drink, police suspected that the can was left by one of the intruders.
The can was bagged as evidence, and in the forensics lab, a DNA sample was obtained from
the lip of the can. The neighborhood was canvassed, and a clerk in a convenience store
remembered selling canned soft drinks to two young males just before the break-in
occurred. The surveillance video in the convenience store was examined, and the clerk
provided the police with the names of all males who were in the store just prior to the
break-in. Three suspects were identified from the surveillance video.
Using a DNA sample found from the soft drink can collected at the crime scene, a PCR was
run to amplify the amount of DNA, and then a DNA profile was performed. Cheek swabs
were obtained from the 3 suspects, and their DNA was tested.
Match the crime scene DNA with a DNA sample from the 3 suspects.
1. Does the crime scene DNA match the DNA from any of the suspects?
2. Is there more than one DNA match?
3. Is this DNA profile sufficient to convict a suspect?
9
Who Are the Parents?
Three baby boys were born on the same morning in the same hospital. That morning, the
hospital had started using new identification bracelets. When the babies were bathed, the
ID bracelets slipped off and the nurses thought a mix-up might have occurred.
Recall that 50 % of a child's DNA is obtained from each parent.
Use a ruler to align the DNA bands of the baby with any DNA bands of the parents.
Determine if any parents share the same band of DNA with the babies.
There is only one correct set of parents matching a baby.
1. Which baby belongs to the Meanys?
2. Which baby belongs to the Glicks?
3. Which baby belongs to the Moes?
4. Is it possible for a child to have a DNA band that is not found in the mother's DNA?
10
Crime Scene DNA Activity
Jimmy Solo, a famous rock star, returned to his New York mansion from an appearance in
Toronto. As Jimmy entered the side entrance he noticed a great mess in the living room and
den. Drawers had been emptied; couch cushions ripped open; the furniture was in disarray
and the wall safe in the study was open. He stormed upstairs to see if his expensive jewelry
collection had been touched and upon doing so heard someone in his bedroom. He grabbed
a small metal statue and rushed into his bedroom surprising the thief. In the ensuing
struggle the thief's gun discharged killing Jimmy instantly.
The next day the housekeeper found Jimmy dead on the floor and immediately contacted
the police. The subsequent investigation identified seven possible suspects.
1. Willie James - lead guitarist in Jimmy's band who was constantly upstaged
and underpaid by Jimmy
2. Samantha Smith - Jimmy's former girlfriend who was dropped by him
following three years of cohabitation
3. Lucifer - Jimmy's bodyguard who is extremely jealous of Jimmy's wealth
4. Jamie Waite - Jimmy's manager who has accumulated massive gambling
debts
5. Dicky Schultz - a former acquaintance of Jimmy's who claims he is owed
thousands for past services
6. Casparina - Jimmy's new girlfriend who is under pressure from former
friends to pay back large loans
7. Jimmy The Weasel - a former friend of Jimmy who was promised a position in
Jimmy's band that never materialized
It was established that all had a motive for killing Jimmy and none had an ironclad alibi.
The police realized they had a problem and consequently decided to undertake a DNA
fingerprinting of all suspects and from a blood sample taken from the crime scene.
11