Dna profiling


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Dna profiling

  1. 1. OVERVIEW • Introduction • Historical Background • Types of DNA profiling • Procedure • Applications
  2. 2. The most powerful and awesome tool acquired by humans since the splitting of atoms” The Time Magazine (U.S.A) “
  3. 3. INTRODUCTION • DNA profiling (also called DNA testing, DNA typing, or genetic fingerprinting) is “technology of using tandem repeats of individuals to identify individuals”
  4. 4. Although the majority of our DNA is the same, there are short pieces called “microsatellites”, which repeats many times in a person’s DNA. It’s the pattern of repeats that are different between individuals. Knowing these microsatellite DNA sequences is the basis of “DNA
  5. 5. WHO INVENTED DNA fingerprinting
  6. 6. university of Leicester, UK in 1985. In 1994,he was knighted by Queen Elizabeth for services to Science and technology.
  7. 7. KEY CONCEPT DNA profiling r finger printing identifies people at molecular level.
  8. 8. can by used for identification. • Based on non coding regions of DNA •Non coding regions have repeating DNA sequences •Number of repeats differs between people •Banding pattern on a gel is a DNA fingerprint
  10. 10. RFLP-based (Restriction fragments length polymorphism) •Original method developed by Alec Jeffreys DNA can be extracted from of DNA •1st step is the Extraction almost any human tissue. Sources of DNA found at a crime scene might include blood, semen, tissue from a deceased victim, cells in a hair follicle, and even saliva. DNA extracted from items of evidence is compared to DNA
  11. 11. DNA EXTRACTION METHOD To extract DNA , most commonly used detergent is Sodium Dodecyl Sulfate
  12. 12. Digestion of proteins and lipids around the cell and it nucleus
  13. 13. DNA is extracted from sample •DNA in the nucleus of the cell is molded, folded, a nd protected by Proteins •Proteinase K is
  14. 14. Ethanol Precipitation The DNA must be purified from the cell extract. Ethanol lowers the effective water concentration, causing large biomolecules to interpenetrate and aggregate. The result is a visible precipitate at the interface, where the ethanol is concentrated.  DNA will rise into the alcohol layer from
  15. 15. Step 2.DNA cuts with the help of Restriction Endonuclease DNA is cut into millions of small fragments with the help of restriction Endonuclease Restriction enzymes chop DNA at specific sequences. the patterns occur in different places in
  16. 16. We are ALL a little bit different! BIG WAQAS’ DNA LITTL E AHMED NAWAZ’ DNA
  17. 17. Our DNA has different sizes of pieces so it makes a different pattern when it’s all WAQAS cut up ’ DNA AHMED NAWAZ’ DNA
  18. 18. RFLP Analysis Everyone has genetic sequences called variable number tandem repeats, or VNTRs – Everyone has different amounts of VNTRs
  19. 19. GEL ELECTROPHORESIS Fragments of DNA from restriction enzyme cleavage are separated from each other when they migrate through a support called an agarose gel – It is similar to the yummy food Jell-O gelatin – It is actually made out of some of the same ingredients • The size-based separation of Molecules
  20. 20. GEL ELECTROPHORESIS The separated DNA fragments are then drawn out of the gel using a nylon membrane • The nylon membrane is treated with chemicals that break the hydrogen bonds in DNA and separate the strands • The single stranded DNA is cross linked to the nylon membrane
  21. 21. DNA having repeat sequences will only be bound to the radioactive or fluorescent probe.
  22. 22. The final step to making a genetic fingerprint is to place a photographic film on top of the nylon surface. The probes leave marks on the film wherever they attached to the RFLPs. Dark bands will then show up when the film is developed, which marks the length of the RFLPs that were hybridized. Researchers are then able to read the fingerprint and match it to others. They do this by
  23. 23. DNA fingerprints can b used to determine which bone fragment belongs to which individual.
  24. 24. STRs & PCR Currently, the most popular method of DNA fingerprinting are short tandem repeats, or STRs for short Unlike VNTRs which analyze minisatellites that have repeat sequences of 9-80 base pairs, STRs use microsatellites which have repeat sequences of only 2-5 base pairs, introducing the “less is more” This was a big step forward in philosophy to the world of DNAforensic science since the length of DNA fingerprinting. fragment being analyzed is short enough to be amplified by polymerase chain reaction (PCR), so now we are able to analyze a very small
  25. 25. PCR was developed in the mid 1980’s and used the same principles that cells use to replicate DNA to amplify the specified region, which is usually between 150-3,000 base pairs in length. STEPS IN PCR OPERATION The solution is heated to 95 C to unzip the double helix DNA structure. • The solution is cooled to 55 C to allow the primers to bind to the ends of the DNA. • The solution is then reheated to 75 C which is the optimal temperature for the Taq polymerase to
  26. 26. ADVANTAGES OF STRs OVER RFLP/VNTR STRs are currently the most popular type of DNA fingerprint, since the whole PCR process takes only a few hours, compared to RFLP/VNTR probe hybridization and film exposure which can take several days. STRs can use much smaller samples ofand quality of the DNA DNA than Thus, the integrity RFLPs/VNTRs, and can factoruse partially even with STRs than sample is not as great a degraded DNA to create a fingerprint with the traditional methods of DNA fingerprinting
  27. 27. DISADVANTAGE OF STRs The only disadvantage of the STR approach is it is sensitive to contaminating DNA, so usually the STR approach is used first, followed by a VNTR analysis if contamination is suspected, and enough DNA is available.
  28. 28. Practical Applications of DNA Fingerprinting Paternity and Maternity Parent-child VNTR pattern analysis has been used to solve standard father-identification cases
  29. 29. Criminal Identification and Forensics DNA isolated from blood, hair, skin cells, or other genetic evidence left at the scene of a crime can be
  30. 30. Diagnosis of Inherited Disorders Diagnose inherited disorders in both prenatal and newborn babies These disorders may include cystic fibrosis, hemophilia, Huntington 's disease, familial
  31. 31. CONCLUSIO N DNA fingerprinting is the most sophisticated way to identify living organisms. DNA cannot easily be altered once it is left at a crimescene or deposited with a mummy, which makes it a strong forensic tool. RFLPs and VNTRs are the traditional methods of fingerprinting DNA, which uses a relatively large sample that uses the method of probe hybridization to detect polymorphisms in the