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 ODWSODWS

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 ODWSODWS

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 ODWSODWS Image Credit: How Stuff WorksHow Stuff Works

Who is the father? Image Credit: How Stuff WorksHow Stuff Works

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 ODWSODWS

..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 ODWSODWS

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 ODWSODWS

Y-chromosome Analysis  Inherited down the paternal line  Complements mtDNA analysis © 2010 Paul Billiet ODWSODWS

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 ODWSODWS