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

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Can also be _______________________ evidence when a small amount is left behind

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

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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

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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

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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)

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o Shorter sequences about 2-5 bases in length are known as _____________

sequences (Short Tandem Repeats)

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 _____________________________

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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 contaminatedo Sneezingo Coughso Evidence collector touches own mouth or nose

To avoid contaminationo Wear disposable gloves and change ofteno Use disposable instruments for handling each sampleo Avoid touching area where DNA may existo Avoid talking, sneezing, coughing over evidenceo Avoid touching face, nose, mouth when collecting and packagingo Air-dry evidence thoroughly before packagingo Place evidence in new paper bags/envelopeso If wet evidence cannot be dried, may be frozen to preserveo Keep evidence cool and dry during transportation and storageo Mold can damage DNAo Avoid plastic bags for DNA evidenceo Direct sunlight and warm conditions can harm DNA

Analysis of DNA FingerprintsWhich man is the father?

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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?

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

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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?

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2. Is there more than one DNA match?

3. Is this DNA profile sufficient to convict a suspect?

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?

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4. Is it possible for a child to have a DNA band that is not found in the mother's DNA?

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 wealth4. Jamie Waite - Jimmy's manager who has accumulated massive gambling

debts5. Dicky Schultz - a former acquaintance of Jimmy's who claims he is owed

thousands for past services6. Casparina - Jimmy's new girlfriend who is under pressure from former

friends to pay back large loans7. Jimmy The Weasel - a former friend of Jimmy who was promised a position in

Jimmy's band that never materializedIt 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.

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