How Is DNA Used in Forensics?
Forensics is the process of applying scientific concepts in a legal context. The most common application of DNA used in forensics is in the analysis of crime scenes. However, the process in also used in civil legal proceedings. Often, forensic analysts are asked to try to resolve the paternity of a child. This is required to determine who is legally responsible for paying child support.
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Function
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To conduct a DNA analysis, samples must be collected and compared. The samples can come from a wide variety of materials, including blood, saliva, skin, finger nails or semen. In criminal investigations, unique DNA sequences, which are called markers, are compared with the markers in DNA samples collected from a suspect or to information contained in a DNA database called Combined DNA Index System (CODIS). In civil cases, such as establishing paternity, the DNA markers are compared between the child and the man believed to be the father.
Identification
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DNA identification consists of analyzing samples to isolate a unique set of DNA markers. An analyst then compares the DNA profiles to ascertain whether a person's DNA sample is a match with the evidence obtained from a crime scene or from family relations. Since a single marker is not enough to determine a match, 13 DNA regions are examined. If there are four or five regions of the DNA samples determined to be similar, it is considered a match.
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Types
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MA analysisultiple types of DN are used in forensics, including Restriction Fragment Length Polymorphism (RFLP), Polymerase Chain Reaction (PCR), Short Tandem Repeat (STR) and Mitochondrial DNA Analysis. RFLP is rarely used because it requires a larger sample size than the other techniques. The PCR method necessitates a very small sample. It can be used to create millions of copies of the DNA sample. A weakness of PCR is that it can be easily contaminated.
STR, which is the most common method of DNA analysis, examines 13 loci or regions within the DNA and basically looks for a match within three or four loci. Mitochondrial DNA Analysis is typically used when the dated is dated or STR and RFLP cannot be used.
Benefits
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DNA used in forensics has yielded benefits in many ways. For example, it has been used to build a record of individuals missing family members as a result of the Holocaust. DNA comparisons have been made to help identify nameless victims buried in graves across the European continent.
Mitochondrial DNA analysis has been used to not only document the migration of the human population around the globe, but also to identify ancestral connections. Many African-Americans who are descendant from African slaves have used this process to narrow the region of the African continent that is the birthplace of their ancestors.
Warning
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It is important that the procedures outlined for collecting and preserving DNA samples be executed according to established protocol. DNA samples used in forensics can be contaminated in a number of ways, including touching, coughing or sneezing near the samples. In addition, analysts may inadvertently add material, such as, fibers, hairs, fluids or other contaminants into the samples.
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