Review on article “Mitochondrial DNA Analysis at the FBI Laboratory”
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Review on article “Mitochondrial DNA Analysis at the FBI Laboratory” by Alice R. Isenberg and Jodi M. Moore.
This article includes an introduction, background and break-down of procedures of used in the laboratory to solve various crimes. The paper explains how mitochondrial DNA or mtDNA is used in criminal investigation with particular reference to missing persons investigations. The background of mitochondrial DNA is discussed, which includes an explanation of what it is and how it is used. The paper explains the difference between traditional DNA and mtDNA, which includes its sequence, location and ‘mode of inheritance’. The paper explains that the nucleus of the cell has two sets of 23 chromosomes, one is maternal and one is paternal. In humans, mitochondrial DNA is inherited strictly through the mother while DNA is paternally inherited. It explains that mtDNA will be identical where there is maternal link without a mutation. This is helpful in that in missing persons any relative with a maternal link is able to provide DNA for the process.
The limitation is that it does not discriminate between various members of the maternal lineage. The mtDNA genome is 16 569 bases in length and has two general regions which are the coding regions and the control region. The paper explains that the coding region is responsible for production of biological molecules while the control region is responsible for the regulation of that molecule. Hypervariable Regions I and II (control and coding regions) both have different base pairs and these are the two regions used for forensic purposes because of the high degree of variability in these regions.
Primary Visual Analysis is part one of the process where the example of a hair comparison is used. This is microscopically compared against a sample group of different hairs. If there is no comparison visually between the known hair and the comparison hair, then the mtDNA is not performed, as there will be a similarity between hairs of the same DNA structure. If the comparison of visual DNA is of tissue samples (bone or tooth and skin), then the basic structure is also microscopically compared and examined for similarities. The second step is to prepare the sample for analysis, cleansing with specialized detergent and placed in an ‘extraction’ solution. If the sample is bone or tooth, then it crushed before being placed in the solution.
The article continues to describe the 6 steps of analysis which include the extraction in step 3 and the amplification of Polymerase Chain Reaction in step 4. Step 4 is enzymatically controlled with duplicate strands being arranged from the existing ones. Step 5 includes the purification and re-amplification of strands in order to minimize mistakes and also to quantify the data gained from the retrieved mtDNA strands. The final step is Sequencing where the mtDNA sequence is created to form a connection between the unknown and the known DNA strands. The dideoxy terminator method is used for this process.
The article is quite a well thought-out explanation of an extremely complicated process. It continues to describe how databases are used to determine population samples and interpretation guidelines that determine protocol for the use of mtDNA which is still relatively new to the scientific world. The process of mtDNA extraction and interpretation is complicated and quite well explained in this article, although a specific interest in this field of inquiry is probably necessary for the full understanding of the process. Separated neatly into the various discussion groups, the various steps are well organized and headed, although it requires movement from the explanation to the diagram via links which disturb the train of thought of the reader. In other words, while one is trying to assimilate the intricacies of the subject, one has to follow web-links to the diagrams. This is not a subject for the average individual unless one is particularly interested in genome theory. For an FBI report it s comparable to scientific journal entries, with marginally less detail given as to processes .
Isenberg, Alice. R. & Moore, Jodi. M. (July 1999). “Mitochondrial DNA Analysis at the FBI Laboratory.” DNA Analysis Unit II, Federal Bureau of Investigation; Washington, DC . U.S Department of Justice, Federal Bureau of Investigation: Volume 1, Number 2.