Introduction to Forensic Science
Developments in genetics have many applications, one of the most important being forensic science. The ability to examine tiny quantities of genetic material left at a crime scene greatly improves the chances of tracking down criminals and proving them guilty. It also allows innocent people accused of crimes to be acquitted and helps establish paternity in relevant lawsuits. Techniques such as genetic fingerprinting could revolutionize the way investigators look at crime.
Genetic fingerprinting, invented by Alec Jeffreys of Leicester University, is a technique exploiting genetic repetitions - parts of DNA sequences whose repetitions vary from person to person. These repetitions can be counted and arranged so that they appear as a bar code unique to each individual. (This is called a multi-locus probe. A single-locus probe works with even smaller DNA samples and produces only two bars, which are still unique to each individual. These are more correctly called genetic profiles.)
The Use of Genetic Fingerprinting
Genetic fingerprinting, though a new technology, has helped to convict thousands, of murderers, rapists, and burglars. It has also acquitted large numbers of of innocent people wrongly believed to have committed a crime. It has also had a huge impact on immigration cases, allowing potential immigrants to prove blood relationship to people who have already gained entry into a country.
Many genetic fingerprints are carried out in lawsuits, most often in paternity suits. Because a genetic fingerprint produces almost unequivocal data, paternity can be assured with an extremely high accuracy rate. This makes these types of suits much easier to handle and adjudicate.
Genetic Fingerprinting: An Historic Example
Genetic fingerprinting tests are an extremely powerful identification tool, as has been shown in forensics and court cases. However, all these cases work with well-preserved samples from relatively recent years. The technique is not limited to these types of samples, though - recently, a genetic fingerprinting test was carried out on the remains of Czar Nicholas, the last czar of Russia, and his family. Though the remains are nearly 80 years old, the test showed with 99.9% accuracy that the remains did, in fact, belong to the czar and his family.
PCR Amplification and Fingerprinting
As exemplified above, genetic fingerprinting is a very powerful tool in the toolbox of forensic scientists, lawyers, and even archaeologists. However, it can be coupled with another powerful technique to create even better results. PCR (polymerase chain reaction) amplification is a process in which a DNA sequence, primer, enzymes, and nucleotides are mixed together, then heated and cooled regularly. This allows millions of copies of the original DNA sequence to be created in a single afternoon. By copying DNA found at a crime scene, then using one of the genetic fingerprinting techniques described above, the chances of finding the perpetrator of a crime are considerably better. The combined techniques have the potential to revolutionize crime investigation, as well as enhancing the abilities of archaeologists and historians.
Created by Kate Stafford and Michael Mannor for ThinkQuest.
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