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Isolation

Identification

Mutation rate

Isolation of Mitochondria from a eukaryotic cell
centrifuge.gif
centrifuge-used to separate cells, organelles depending upon their density


The isolation of intact mitochondria was first carried out by the zonal centrifugal method that was developed in 1948, it was also the first component of the human genome to be fully sequenced. The amount of mitochondrial DNA located with a cell varies upon the type of tissue that is used. Cells that are metabolically active require large numbers of mitochondria and are a more reliable specimens to use, tissues such as muscle, liver, cardiac or bone are typically used. Within forensics, bone is the most used tissue in analysis, due to mtDNA analysis only applied if the corpse is heavily degraded resulting in nuclearDNA unsuitable or the identity cannot be identified. Tissue samples that have been heat treated prove the hardest to identify as a result of the cell wall lysing and the DNA being denatured at temperatures above 60°C.

For bone fragments, the sample is ground to dust, detergent is added to help the denaturing of the lipid layer and the chromosomal proteins, releasing the DNA into solution, the mitochondrial lipid layer is better protected with the double layer and withstands the denaturing. The sample is centrifuged for a short period, insufficient to separate all the contents from the solute, the organelles are separated depending upon their constituent mass the organelles are isolated with some other organelles but mitochondria are the only organelle with DNA to be isolated.