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Dna fingerprinting powerpoint

1. 1. DNA ProfilingDNA Profiling (DNA fingerprinting)(DNA fingerprinting)
2. 2. What is DNA Profiling?What is DNA Profiling? A technique used by scientists toA technique used by scientists to distinguish between individuals of thedistinguish between individuals of the same species using only samples of theirsame species using only samples of their DNA.DNA. The only difference between peopleThe only difference between people (or any animal) is the order of the(or any animal) is the order of the base pairsbase pairs. The information contained in. The information contained in DNA is determined primarily by theDNA is determined primarily by the sequence of letters along the zipper. Thesequence of letters along the zipper. The different sequences is the same as thedifferent sequences is the same as the word "POST" has a different meaningword "POST" has a different meaning from "STOP" or "POTS," even thoughfrom "STOP" or "POTS," even though they use the same lettersthey use the same letters
3. 3. 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 the University ofUniversity of Leicester in 1985.Leicester in 1985.  He was knighted inHe was knighted in 1994.1994.
4. 4. Stages of DNA ProfilingStages of DNA Profiling  Stage 1Stage 1:: Cells are broken downCells are broken down to release DNAto release DNA If only a small amountIf only a small amount of DNA is available itof DNA is available it can be amplified usingcan be amplified using the polymerase chainthe polymerase chain reaction (PCR)reaction (PCR)
5. 5. Stages of DNA ProfilingStages of DNA Profiling  Step 2:Step 2: The DNA is cut into fragments usingThe DNA is cut into fragments using restrictionrestriction enzymesenzymes.. Each restriction enzyme cuts DNA at a specific baseEach restriction enzyme cuts DNA at a specific base sequence.sequence.
6. 6. Stages of DNA ProfilingStages of DNA Profiling  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 sizesfragments of all different sizes 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).
7. 7. Stages of DNA ProfilingStages of DNA Profiling Stage 3:Stage 3:  Fragments areFragments are separated on theseparated on the basis of size usingbasis of size using a process calleda process called gelgel electrophoresis.electrophoresis.  DNA fragments areDNA fragments are injected into wellsinjected into wells and an electricand an electric current is appliedcurrent is applied along the gel.along the gel.
8. 8. Stages of DNA ProfilingStages of DNA Profiling DNA is negativelyDNA is negatively charged so it ischarged so it is attracted to theattracted to the positive end of thepositive end of the gel.gel. The shorter DNAThe shorter DNA fragments movefragments move faster than thefaster than the longer fragments.longer fragments. DNA is separated onDNA is separated on basis of size.basis of size.
9. 9. Stages of DNA ProfilingStages of DNA Profiling  A radioactive materialA radioactive material is added whichis added which combines with the DNAcombines with the DNA fragments to produce afragments to produce a fluorescent image.fluorescent image.  A photographic copy ofA photographic copy of the DNA bands isthe DNA bands is obtained.obtained.
10. 10. Stages of DNA ProfilingStages of DNA Profiling Stage 4:Stage 4:  The pattern of fragment distributionThe pattern of fragment distribution is then analysed.is then analysed.
11. 11. Uses of DNA ProfilingUses of DNA Profiling  DNA profiling isDNA profiling is used to solveused to solve crimescrimes andand medicalmedical problemsproblems
12. 12. CrimeCrime  Forensic science is the use ofForensic science is the use of scientific knowledge in legalscientific knowledge in legal situations.situations.  The DNA profile of each individual isThe DNA profile of each individual is highly specific.highly specific.  The chances of two people havingThe chances of two people having exactlyexactly the same DNA profile isthe same DNA profile is 30,000 million to 1 (except for30,000 million to 1 (except for identical twins).identical twins).
13. 13. Biological materials used for DNABiological materials used for DNA profilingprofiling  BloodBlood  HairHair  SalivaSaliva  SemenSemen  Body tissue cellsBody tissue cells  DNA samples haveDNA samples have been obtained frombeen obtained from vaginal cellsvaginal cells transferred to thetransferred to the outside of a condomoutside of a condom during sexualduring sexual intercourse.intercourse.
14. 14. DNA Profiling can solve crimesDNA Profiling can solve crimes  The pattern of the DNA profile is thenThe pattern of the DNA profile is then compared with those of the victim and thecompared with those of the victim and the suspect.suspect.  If the profileIf the profile matchesmatches the suspect itthe suspect it provides strong evidence that the suspectprovides strong evidence that the suspect was present at the crime scene (was present at the crime scene (NB:itNB:it does not prove they committed thedoes not prove they committed the crime).crime).  If the profileIf the profile doesn’tdoesn’t match the suspectmatch the suspect then that suspect may be eliminated fromthen that suspect may be eliminated from the enquiry.the enquiry.
15. 15. ExampleExample  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 sample, the victim and ablood sample, the victim and a suspect as follows:suspect as follows:
16. 16. Was the suspect at the crime scene?Was the suspect at the crime scene? Suspects Profile Blood sample from crime scene Victims profile
17. 17. Solving Medical ProblemsSolving Medical Problems 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) and maternity(mother) can be determined.maternity(mother) can be determined. This information can be used inThis information can be used in • Paternity suitsPaternity suits • Inheritance casesInheritance cases • Immigration casesImmigration cases
18. 18. Example: A Paternity TestExample: A Paternity Test  By comparing the DNA profile of aBy 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 child which 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.
19. 19. Is this man the father of the child?Is this man the father of the child? Mother Child Man
20. 20. Personal IdentificationPersonal Identification  The notion of using DNA fingerprints as a sortThe notion of using DNA fingerprints as a sort of genetic bar code toof genetic bar code to identify individualsidentify individuals hashas been discussedbeen discussed  Diagnosis of Inherited DisordersDiagnosis of Inherited Disorders  diagnosis inherited disordersdiagnosis inherited disorders in bothin both prenatalprenatal andand newborn babiesnewborn babies  These disorders may include cystic fibrosis,These disorders may include cystic fibrosis, hemophilia, Huntingtons disease, familialhemophilia, Huntingtons disease, familial Alzheimers, sickle cell anemia, thalassemia,Alzheimers, sickle cell anemia, thalassemia, and many others.and many others.
21. 21.  In 2002 ElizabethIn 2002 Elizabeth Hurley used DNAHurley used DNA profiling to proveprofiling to prove that Steve Bingthat Steve Bing was the fatherwas the father of her child Damienof her child Damien
22. 22. DNA Fingerprinting using VNTRsDNA Fingerprinting using VNTRs  On some human chromosomes, a short sequence ofOn some human chromosomes, a short sequence of DNA has been repeated a number of times.DNA has been repeated a number of times.  the repeat number may vary from one to thirty repeatsthe repeat number may vary from one to thirty repeats  these repeat regions are usually bounded by specificthese repeat regions are usually bounded by specific restriction enzyme sitesrestriction enzyme sites  cut out the segment of the chromosome containingcut out the segment of the chromosome containing thisthis variable number of tandem repeatsvariable number of tandem repeats ((VNTRsVNTRs ))  identify the VNTRs for the DNA sequence of theidentify the VNTRs for the DNA sequence of the repeat.repeat.
23. 23. Famous CasesFamous Cases  Colin Pitchfork wasColin Pitchfork was the first criminalthe first criminal caught based oncaught based on DNA fingerprintingDNA fingerprinting evidence.evidence.  He was arrested inHe was arrested in 1986 for the rape1986 for the rape and murder of twoand murder of two girls and wasgirls and was sentenced in 1988.sentenced in 1988.