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Transcript of DNA "FINGERPRINTING"
BY DRAKE SEVERINSKY
Where is DNA fingerprinting used?
DNA "fingerprinting" is used mostly in law enforcement to solve crimes. It is even being used in many courts all over the world in paternity testing and for determining family relations. Even reality shows like Dr. Phil have been known to use this test.
In 1984, Alec Jefferys , a British scientist, found DNA sequences he called minisatellites that don't contribute to how the gene works but are repeated in the gene. Each person has a unique pattern of minisatellites with the exception of identical twins.
3. The DNA band pattern is transferred
a nylon membrane.
5. The excess probe material is washed away leaving a unique DNA band pattern.
6. The DNA pattern is then transferred to X-ray film. When developed the resultant visible pattern is the DNA fingerprint. This will look like a grocery store bar code.
The data base for DNA "fingerprinting" is a computer. All the information gotten from the samples from the crime scene are analyzed and put in the computer. When suspect's DNA is analyzed it is compared to the samples already obtained and when a match is detected the police can pursue this person of interest further.
How Good It Is?
DNA fingerprinting is the most accurate test there is especially with the many improvements made over the years. It is 99.9% accurate. But the test is only as good as the quality of the sample used. ie. a sample from a live person is better than one from a dead person.
The Down Side
The use of the conventional fingerprint became popular in the 1930's and is still used today. However it can be altered and this is a huge disadvantage.
The new DNA fingerprint became popular in the 1980's and is now used all the time to solve crimes. The big advantage to this is that it can't be altered.
DNA fingerprinting = DNA typing
Definition- a method of isolating and then making images of sequences of DNA.
1. Get a sample (blood, skin, hair) from which DNA can be extracted.
2. DNA is cut with restriction enzymes into fragments which are then separated into bands by electrophoresis on an agarose gel.
4. A radioactive DNA probe is added which will bind to specific DNA sequences or minisatellites on the nylon membrane.
As previously mentioned the quality of the sample is important. Any contamination will change the findings. Also how the test is performed can affect the results. That is why testing is usually done in duplicate and by different people. Finally just because the DNA evidence strongly suggests a person of interest, all the rest of the evidence obtained has to make sense.
DNA Fingerprinting Animation-
Betsch, David F (November 1994) DNA fingerprinting in human health and society-
(2011) DNA profiling-