Mitochondrial DNA analysis can provide evidential results and reveal lineage through a person’s maternal line, making it valuable in solving cold cases. It is more abundant and less likely to degrade than nuclear DNA, and can be used to identify missing persons or unidentified remains. It has been used to identify historical figures such as Jesse James and Tsarina Alexandra Romanova, and can also be used with animal DNA to trace species across generations.
In forensic labs, DNA samples sometimes arrive degraded and little viable testing material is left. Mitochondrial DNA analysis analyzes the DNA present in a cell’s mitochondria, rather than the nuclear DNA that most tests are designed for. This technique can provide evidential results and also reveal lineage through a person’s or species’ maternal line.
Nuclear DNA is found only in the nucleus of cells, one copy each from the father and mother. Mitochondria produce energy within cells and are present in large numbers. In samples with no or degraded nuclear DNA, the increased amount of mitochondrial DNA (mtDNA) means the test can still be performed. Hair, bone and teeth are good candidates for mitochondrial DNA analysis. In a case where most of a body has decayed or perhaps burned, bones and teeth are often all that is left.
Restriction Fragment Length Polymorphism (RFLP) and Short Tandem Repeat (STR) analysis, the most commonly performed, test only nuclear DNA. MtDNA is not only more abundant, but it’s also transported deeper within cells, so it’s less likely to be destroyed when the cell is compromised. It does not degrade even when the sample is old. This makes mitochondrial DNA analysis an extremely valuable tool in solving cold cases.
Testing begins with sample collection and documentation. Photographs are taken because the process will destroy the material. Once the visual inspection is complete, the sample is carefully cleaned to remove any contaminants that could affect the results. The sample will then be processed to make many copies of the DNA, which can be analyzed and compared to a control.
All those maternally related, such as siblings who have the same mother, will have the exact same mtDNA, although the analysis cannot distinguish individuals. It is often used in missing persons cases or in the discovery of unidentified remains because a surviving maternal relative can provide a comparison sample. Mitochondrial DNA analysis can also be done with animal DNA and helps scientists trace species across generations.
Mitochondrial DNA analysis has been used to identify the remains of US outlaw Jesse James, as well as Tsarina Alexandra Feodorovna Romanova and her children. Ana Anderson, a woman who claimed to be the daughter of Empress Anastasia who survived the family’s execution, was discredited after her mtDNA showed her to be a Pole named Franzisca Schonzkowska. Analysis of preserved heart tissue from a child purported to be Marie Antoinette’s son Louis Charles, who died in prison during the French Revolution, and mtDNA from the queen’s hair showed the child was most likely the unfortunate prince.
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