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DNA ForensicDNA Forensic

IdentificationIdentification

Ashley KowaleskiAshley Kowaleski

I400I400

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ObjectivesObjectives

What is forensic science?What is forensic science?

How and when did forensics begin?How and when did forensics begin?

When was DNA identification discovered?When was DNA identification discovered? What is DNA identification used to determine?What is DNA identification used to determine?

What exactly are forensic scientist looking for?What exactly are forensic scientist looking for?

What is the process does DNA identificationWhat is the process does DNA identification

involve?involve? How are criminals processed?How are criminals processed?

What is the outlook for the future?What is the outlook for the future?

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Forensic ScienceForensic Science

Process of gathering and examiningProcess of gathering and examiningevidence of a crimeevidence of a crime

First practiced forensic medicine in 1958First practiced forensic medicine in 1958

ItalyItaly

Application of medical knowledge to legalApplication of medical knowledge to legalquestionsquestions

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Unique IdentifiersUnique Identifiers

FingerprintsFingerprints When a persons handWhen a persons hand

touched a surface, it left atouched a surface, it left a

barely visible markbarely visible mark Each persons fingerprintEach persons fingerprint

is a unique identifier ofis a unique identifier ofthat person, no twothat person, no twopeoples are alikepeoples are alike

DNADNA Genetic material that isGenetic material that is

found in DNA is also afound in DNA is also a

unique identifierunique identifier Not until1985 when DNANot until1985 when DNA

became part of forensicbecame part of forensicsciencescience

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DNADNA (deoxyribonucleic acid)(deoxyribonucleic acid)

Nucleic acid that carries the genetic informationNucleic acid that carries the genetic information

Double helixDouble helix

2 long chains of nucleotides twisted and joined2 long chains of nucleotides twisted and joinedby hydrogen bondsby hydrogen bonds

Can be found in white blood cellsCan be found in white blood cells

Polymorphic: vary in shape from person toPolymorphic: vary in shape from person to

personperson

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Short Tandem RepeatsShort Tandem Repeats

(STR)(STR) STR regions are nucleotides along the backbone of aSTR regions are nucleotides along the backbone of a

chromosomechromosome

13 markers used in forensic science13 markers used in forensic science

Classified into groups depending on the size of theClassified into groups depending on the size of therepeat regionsrepeat regions Mini satellitesMini satellites

Micro satellitesMicro satellites

The chance that any two peoples DNA fingerprint for aT

he chance that any two peoples DNA fingerprint for aparticular set of regions is exceptionally smallparticular set of regions is exceptionally small 1/101/10thth of a single % of DNA, about 3 million bp, differ from oneof a single % of DNA, about 3 million bp, differ from one

person to the nextperson to the next

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The ProcessThe Process

IsolationIsolation

QuantifyingQuantifying

Polymerase Chain Reaction (PCR)Polymerase Chain Reaction (PCR)

Short Tandem RepeatShort Tandem Repeat--Polymerase ChainPolymerase ChainReaction (STRReaction (STR--PCR)PCR)

InterpretationInterpretation

DatabaseDatabase

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IsolationIsolation

Scientist extract DNA from the nucleus ofScientist extract DNA from the nucleus ofcells in tissuecells in tissue

Quality of tissue DNA samples degradesQuality of tissue DNA samples degradesas body decomposesas body decomposes

11--4 hours4 hours

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QuantifyingQuantifying

Tests are run to determine the amount ofTests are run to determine the amount ofDNA recoveredDNA recovered

Targeted amount 1 nanogram (billionth ofTargeted amount 1 nanogram (billionth ofa gram)a gram)

If inadequate quantity, isolation must beIf inadequate quantity, isolation must be

repeatedrepeated 11--2 hours2 hours

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Polymerase ChainPolymerase Chain

Reaction (PCR)Reaction (PCR) One of the most popular and widely usedOne of the most popular and widely used

techniques in molecular biologytechniques in molecular biology

Reproduces millions of exact copies ofReproduces millions of exact copies ofspecific fragments of DNAspecific fragments of DNA

Enables even highly degraded samplesEnables even highly degraded samples

to be analyzedto be analyzed 3 hours3 hours

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Polymerase Chain ReactionPolymerase Chain Reaction

(PCR)(PCR)

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Polymerase ChainPolymerase Chain

Reaction (PCR)Reaction (PCR) Based on polymerase enzymeBased on polymerase enzyme

Break apart double helix, two single strandsBreak apart double helix, two single strands

Rebuild two strands into two complete helixesRebuild two strands into two complete helixes DNA deposited into polymerases andDNA deposited into polymerases and

nucleotidesnucleotides

Repeated rapidly, doubling amount of DNARepeated rapidly, doubling amount of DNA

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STRSTR--PCRPCR

Mainly same processMainly same process

Focus solely on STR regionsFocus solely on STR regions

Since these repeat regions are usuallySince these repeat regions are usuallybounded by specific restriction enzymebounded by specific restriction enzymesites, it is possible to cut out the segmentsites, it is possible to cut out the segment

of the chromosomeof the chromosome

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Capillary ElectrophoresisCapillary Electrophoresis

(CE)(CE) Early 1990sEarly 1990s Automated analytical techniqueAutomated analytical technique Generally used for separating ions, which move atGenerally used for separating ions, which move at

different speeds when the voltage is applied dependingdifferent speeds when the voltage is applied dependingon their size and charge. The solutes are seen ason their size and charge. The solutes are seen aspeaks as they pass through the detectorpeaks as they pass through the detector

Area of each peak is proportional to their concentrationArea of each peak is proportional to their concentration Produces a chart mapping a persons exact geneticProduces a chart mapping a persons exact genetic

makeupmakeup This is the information used to compare suspects to aThis is the information used to compare suspects to a

crimecrime http://chemi.muni.cz/~analytika/ce/cehttp://chemi.muni.cz/~analytika/ce/ce--animation.gifanimation.gif

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Capillary ElectrophoresisCapillary Electrophoresis

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InterpretationInterpretation

A DNA scientist reviews the DNA profileA DNA scientist reviews the DNA profileproduced through the capillary electrophoresisproduced through the capillary electrophoresis

to determine if there is a matchto determine if there is a match STR markers are examined (2STR markers are examined (2--5 bp)5 bp)

11--3 are not enough to determine is the sample3 are not enough to determine is the samplecame from the suspectcame from the suspect

44--5, beyond a reasonable doubt5, beyond a reasonable doubt

5 very rare5 very rare

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National DNA Databank:National DNA Databank:

CODISCODIS TheThe COCOmbinedmbined DDNANA IIndexndex SSystemystem

Blends computer and DNA technologies into aBlends computer and DNA technologies into a

tool for fighting crimetool for fighting crime 2 indexes2 indexes

Convicted Offender IndexConvicted Offender Index DNA profiles of individuals convicted of criminal crimesDNA profiles of individuals convicted of criminal crimes

Forensic IndexForensic Index DNA profiles developed from crime scene evidenceDNA profiles developed from crime scene evidence

All profiles stored in CODIS are generatedAll profiles stored in CODIS are generatedusing STR analysisusing STR analysis

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The FutureThe Future

March 2004: President Bush proposedMarch 2004: President Bush proposed$1 billion in funding over the next 5 years$1 billion in funding over the next 5 years

Reduce DNA testing backlogReduce DNA testing backlog

Build crime lab capacityBuild crime lab capacity

Stimulate research and developmentStimulate research and development

Support trainingSupport training Protect the innocentProtect the innocent

Identify missing personsIdentify missing persons