Forensic DNA

DNA profiling (also called DNA fingerprinting, DNA testing, or DNA typing) is a forensic technique used to identify individuals by characteristics of their DNA. A DNA profile is a small set of DNA variations that is very likely to be different in all unrelated individuals, thereby being as unique to individuals as are fingerprints (hence the alternate name for the technique). DNA profiling should not be confused with full genome sequencing. First developed and used in 1984, DNA profiling is used in, for example, parentage testing and criminal investigation, to identify a person or to place a person at a crime scene, techniques which are now employed globally in forensic science to facilitate police detective work and help clarify paternity and immigration disputes. DNA fingerprinting has also been widely used in the study of animal and floral populations and has revolutionized the fields of zoology, botany, and agriculture.

Although 99.9% of human DNA sequences are the same in every person, enough of the DNA is different that it is possible to distinguish one individual from another, unless they are monozygotic ("identical") twins. DNA profiling uses repetitive ("repeat") sequences that are highly variable, called variable number tandem repeats (VNTRs), in particular short tandem repeats (STRs), also known as microsatellites, and minisatellites. VNTR loci are very similar between closely related individuals, but are so variable that unrelated individuals are extremely unlikely to have the same VNTRs.

The modern process of DNA profiling was developed in 1984 by Sir Alec Jeffreys while working in the Department of Genetics at the University of Leicester.

Developed by Professor of Genetics Sir Alec Jeffreys, the process begins with a sample of an individual's DNA (typically called a "reference sample"). A common method of collecting a reference sample is the use of a buccal swab, which is easy, non-invasive and cheap. When this is not available (e.g. because a court order is needed but not obtainable) other methods may need to be used to collect a sample of blood, saliva, semen, vaginal lubrication, or other appropriate fluid or tissue from personal items (e.g. a toothbrush, razor) or from stored samples (e.g. banked sperm or biopsy tissue). Samples obtained from blood relatives (related by birth, not marriage) can provide an indication of an individual's profile, as could human remains that had been previously profiled.

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