DNA Fingerprinting powerpoint.ppt

7/17/2019 DNA Fingerprinting powerpoint.ppt

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DNA ProfilingDNA Profiling(DNA fingerprinting)(DNA fingerprinting)



What is DNA Profiling?What is DNA Profiling?

A technique used by scientists toA technique used by scientists todistinguish between individuals ofdistinguish between individuals of

the same species using only samplesthe same species using only samples

of their DNAof their DNA



Who Invented it?Who Invented it?

The process of DNAThe process of DNA

fingerprinting wasfingerprinting was

invented by Alecinvented by Alec

Jeffreys at theJeffreys at theUniversity ofUniversity of

eicester in !"#$%eicester in !"#$%

&e was 'nighted in&e was 'nighted in

!""%!""%



Stages of DNA ProfilingStages of DNA Profiling

Stage 1Stage 1

*ells are bro'en down*ells are bro'en down

to release DNAto release DNA

+f only a small amount+f only a small amount

of DNA is available itof DNA is available it

can be amplified usingcan be amplified using

the polymerase chainthe polymerase chainreaction (,*-)reaction (,*-)




Step 2:Step 2:

The DNA is cut into fragments usingThe DNA is cut into fragments using restrictionrestrictionenzymesenzymes%%

.ach restriction en/yme cuts DNA at a specific base.ach restriction en/yme cuts DNA at a specific basesequence%sequence%




The sections of DNA that are cut outThe sections of DNA that are cut out

are calledare called restriction fragments.restriction fragments.

This yields thousands of restrictionThis yields thousands of restriction

fragments of all different si/esfragments of all different si/es

because the base sequences beingbecause the base sequences being

cut may be far apart (long fragment)cut may be far apart (long fragment)

or close together (short fragment)%or close together (short fragment)%




Stage 3:Stage 3: 0ragments are0ragments are

separated on theseparated on the

basis of si/e usingbasis of si/e usinga process calleda process called gelgelelectrophoresis%electrophoresis%

DNA fragments areDNA fragments are

in1ected into wellsin1ected into wellsand an electricand an electriccurrent is appliedcurrent is appliedalong the gel%along the gel%




DNA is negativelyDNA is negativelycharged so it ischarged so it isattracted to theattracted to the

positive end of thepositive end of thegel%gel%

The shorter DNAThe shorter DNAfragments movefragments move

faster than thefaster than thelonger fragments%longer fragments%

DNA is separated onDNA is separated onbasis of si/e%basis of si/e%




A radioactiveA radioactive

material is addedmaterial is added

which combineswhich combines

with the DNAwith the DNAfragments tofragments to

produce aproduce a

fluorescent image%fluorescent image%

A photographicA photographiccopy of the DNAcopy of the DNA

bands is obtained%bands is obtained%




Stage 4:Stage 4:

The pattern of fragment distributionThe pattern of fragment distribution

is then analysed%is then analysed%



Uses of DNA ProfilingUses of DNA Profiling

DNA profiling isDNA profiling is

used to solveused to solve

crimescrimes andand

medicalmedical

problemsproblems



CrimeCrime

0orensic science is the use of0orensic science is the use ofscientific 'nowledge in legalscientific 'nowledge in legalsituations%situations%

The DNA profile of each individual isThe DNA profile of each individual ishighly specific%highly specific%

The chances of two people havingThe chances of two people having

e2actlye2actly the same DNA profile isthe same DNA profile is345444 million to ! (e2cept for345444 million to ! (e2cept foridentical twins)%identical twins)%



Biological materials used for DNABiological materials used for DNA

profilingprofiling 6lood6lood &air&air 7aliva7aliva

7emen7emen 6ody tissue cells6ody tissue cells DNA samples haveDNA samples have

been obtained frombeen obtained fromvaginal cellsvaginal cells

transferred to thetransferred to theoutside of a condomoutside of a condomduring se2ualduring se2ualintercourse%intercourse%



DNA Profiling can solve crimesDNA Profiling can solve crimes

The pattern of the DNA profile is thenThe pattern of the DNA profile is thencompared with those of the victim and thecompared with those of the victim and thesuspect%suspect%

+f the profile+f the profile matchesmatches the suspect itthe suspect itprovides strong evidence that the suspectprovides strong evidence that the suspectwas present at the crime scene (was present at the crime scene (NB:itNB:itdoes not prove they committed thedoes not prove they committed the

crime).crime).

+f the profile+f the profile doesn8tdoesn8t match the suspectmatch the suspectthen that suspect may be eliminated fromthen that suspect may be eliminated fromthe enquiry%the enquiry%



EampleEample

A violent murder occurred%A violent murder occurred%

The forensics team retrieved a bloodThe forensics team retrieved a blood

sample from the crime scene%sample from the crime scene%

They prepared DNA profiles of theThey prepared DNA profiles of the

blood sample5 the victim and ablood sample5 the victim and a

suspect as followssuspect as follows



Was the suspect at the crimeWas the suspect at the crime

scene?scene?

7uspects,rofile

6lood samplefrom crimescene

9ictimsprofile



Solving !edical Pro"lemsSolving !edical Pro"lems

DNA profiles can be used to determineDNA profiles can be used to determine

whether a particular person is the parentwhether a particular person is the parent

of a child%of a child%

A childs paternity (father) andA childs paternity (father) andmaternity(mother) can be determined%maternity(mother) can be determined%

This information can be used inThis information can be used in

:

,aternity suits,aternity suits: +nheritance cases+nheritance cases

: +mmigration cases+mmigration cases



Eample# A Paternit$ %estEample# A Paternit$ %est

6y comparing the DNA profile of a6y comparing the DNA profile of a

mother and her child it is possible tomother and her child it is possible to

identify DNA fragments in the childidentify DNA fragments in the childwhich are absent from the mother andwhich are absent from the mother and

must therefore have been inheritedmust therefore have been inherited

from the biological father%from the biological father%



Is this man the father of the child?Is this man the father of the child?

;other *hild ;an



&amous cases&amous cases

+n <44< .li/abeth+n <44< .li/abeth

&urley used DNA&urley used DNA

profiling to proveprofiling to prove

that 7teve 6ingthat 7teve 6ingwas the fatherwas the father

of her child Damienof her child Damien



&amous Cases&amous Cases

*olin ,itchfor' was*olin ,itchfor' was

the first criminalthe first criminal

caught based oncaught based on

DNA fingerprintingDNA fingerprintingevidence%evidence%

&e was arrested in&e was arrested in

!"#= for the rape!"#= for the rape

and murder of twoand murder of twogirls and wasgirls and was

sentenced in !"##%sentenced in !"##%



&amous Cases&amous Cases

>%J% 7impson was>%J% 7impson wascleared of a doublecleared of a doublemurder charge inmurder charge in!"" which relied!"" which reliedheavily on DNAheavily on DNAevidence%evidence%

This caseThis casehighlighted labhighlighted labdifficulties%difficulties%



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''')'orldofteaching)com

http#**''')'orldofteaching)com is home to over a

thousand po'erpoints su"mitted "$ teachers) %his is a

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