DNA fingerprinting

Discovered in 1984, DNA fingerprinting would change the world of forensics. Today it is used to identify bodies, track down relatives, and find cures for diseases by taking a closer look at DNA sequences because they are so unique. Using DNA fingerprinting, many criminal cases have been solved bringing justice to the world. It has also reunited families after certain disasters. Affecting the agricultural and medical fields as well by diagnosing disorders and genetically modified organisms, DNA fingerprinting has a wide range of influence.

Discovery of DNA Fingerprinting
Alec Jeffreys, a 27 year old researcher at the University of Leicester, studied the inherited variation of genes, trying to solve problems over immigration and paternity. Jeffreys soon shifted his focus to DNA. On September 10, 1984, he created the first every genetic fingerprint when he learned that the length of every person's Variable Number of Tandem Repeats (VNTRs) were different, making it possible to identify somebody. Genetic fingerprinting was soon tested when two young girls were raped and murdered in a location near the University of Leicester. Blood was tested by numerous suspects and would eventually lead to the solving of the crimes. As a result Alec Jeffreys was knighted by the Queen of England for his dramatic discovery that would better the problems referring to crime, immigration, and much more.

Uses
Two main methods for DNA fingerprinting exist; restriction fragment length polymorphism (RFLP) and polymerase chain reaction (PCR). Identified based off of the size and repeating sequences of their DNA, each method works when searching through the single nucleotide polymorphisms (SNPs) or the short tandem repeats (STRs). DNA fingerprinting is commonly used in forensics, noncriminal identification, agriculture, and medicine.

DNA fingerprinting is a common technique used in forensics to detect crime. All it needs is a little bit of DNA to determine a suspect guilty for a crime, which can be used for present daycrimes but also for criminal cases that are years old. Another way it is used in forensics is to identify a dead body in certain situations. Another common use of DNA fingerprinting is noncriminal identification. Noncriminal identification allows parents to know whether a child is theirs in a quick and orderly manner. This techniques finds a parent of a child and requires them to provide financial support for the child. This technique also helps in adoption cases and inheritance cases, establishing more relationships. During disasters around the world such as wars and earthquakes, children are often separated from their parents. DNA fingerprinting is then used to identify the families, reuniting them. A third technique where DNA fingerprinting is commonly used is in the medicine field. When finding a donor for blood or bone marrow donations, doctors often need to use DNA fingerprinting to find a good genetic match. Doctors also use DNA fingerprinting to personalize a cancer patient's treatment based off of their genes. Another common use of DNA fingerprinting in medicine is to label tissue samples correctly with the right name. A final use of DNA fingerprinting is in the agricultural industry. DNA fingerprinting can be used to determine a genetically modified organism or plants that can be used to cure a disease. Among animals, DNA fingerprinting can be used to prove whether an animal is purebred or not, a common method used among horses that compete in races.

When testing humans, blood or saliva is normally tested, neither being better or more accurate than the other. However, the saliva samples must be stored or test take place in a quick and orderly fashion or else bacteria may interfere with the DNA samples. The saliva samples may not contain any DNA so a test may need to take place again.

Making DNA Fingerprints
Agarose gels, derived from seaweed, are gels used in the gel electrophoresis process. Commonly, around 1% of the solution is agarose. So in there would be around 1 gram of agarose in 100 mL of [TAE]. TAE acts as a buffer and includes Tris base, acetic acid, and EDTA. The solution is heated up, becoming a warm liquid and the agarose and TAE is mixed. While the agarose solution cools down, a casting trey is tapes around the edges so that there is no leakage of any sort. The solution is poured into the trey with combs inside, that will form wells as the solution hardens. After the gel hardens, it is submerged into water where the DNA samples can be pipetted into the wells.

After the samples of DNA are collected, they are stored and dissolved in water. Restriction enzymes are normally added to the liquid sample, cutting up the strands of DNA. This is done because without the restriction enzymes, the DNA is still too long. After a couple hours, the restriction enzyme cuts the the DNA into around 5-10 base pairs. With a pipette, the samples are injected into wells of the gels, and after running an electric current through the gel, the DNA strands are separated based off its size. This process is called gel electrophoresis. When completed, the gels are often placed on ultraviolet light to make the dye mixed with the DNA stand out. This process may be repeated to find more accurate results, but the strips' patterns of DNA in the gel are used to find the result.

Video
More information on how DNA Fingerprinting works. ZxWXCT9wVoI