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DNA profiling

DNA profiling. Aka DNA finger printing. We’re all (nearly) unique. Most DNA is highly conservative from one person to the next A few small domains (0.1%) are very variable. © 2010 Paul Billiet ODWS. Applications. Crime scene investigations Paternity suites and family relationships

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DNA profiling

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  1. DNA profiling Aka DNA finger printing

  2. We’re all (nearly) unique • Most DNA is highly conservative from one person to the next • A few small domains (0.1%) are very variable © 2010 Paul Billiet ODWS

  3. Applications • Crime scene investigations • Paternity suites and family relationships • Archaeology • Human/family ancestry • Exonerate persons wrongly accused of crimes • Identify catastrophe victims • Identify endangered and protected species as an aid to wildlife officials (could be used for prosecuting poachers) • Detect bacteria and other organisms that may pollute air, water, soil, and food • Match organ donors with recipients in transplant programs • Determine pedigree for seed or livestock breeds • Authenticate consumables such as caviar and wine © 2010 Paul Billiet ODWS

  4. Procedure • Sample of tissue or cell • DNA extracted • DNA amplified by PCR • DNA fragmented using restriction enzymes • Gene probes added to identify fragments • Patterns of fragments of DNA of known origin & unknown compared • Control fragments of DNA and ladders used © 2010 Paul Billiet ODWS Image Credit: How Stuff Works

  5. Who is the father? Image Credit: How Stuff Works

  6. Restriction Fragment Length Polymorphism (RFPL) • Restriction enzymes cut the DNA at particular base sequences • The presence or absence of these sequences in the genome will give different lengths of DNA fragments when they are cut using a particular restriction enzyme • The DNA fragments are separated by electrophoresis • DNA probes identify the sequences • Patterns of DNA fragments on the gel can by used to compare DNA from different samples Southern Blotting © 2010 Paul Billiet ODWS

  7. ..gatagatagatagatagatagatagatagata.. • Short Tandem Repeats (STRs) • Within the human genome there are regions where a short base sequence is repeated many times • The number of repeats is very variable • Identified repeats are cut out using a restriction enzyme • The DNA fragments separated by electrophoresis • The different repeats are identified by DNA probes with radioactive or fluorescent markers • Samples with the same STRs will show the same pattern in on the electrophoresis gel © 2010 Paul Billiet ODWS

  8. Mitochondrial DNA Analysis • Mitochondrial DNA (mtDNA) • Useful for analysing older tissue samples • Useful for analysing hair, bones or teeth • Inherited down the maternal line © 2010 Paul Billiet ODWS

  9. Y-chromosome Analysis • Inherited down the paternal line • Complements mtDNA analysis © 2010 Paul Billiet ODWS

  10. Problems • Cost • Today limited to matches with 4 to 6 probes • Few probes = greater chance of miss match • Contamination of samples • Degradation of DNA with time © 2010 Paul Billiet ODWS

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