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What is the Mitochondria?

written by: •edited by: Paul Arnold•updated: 1/9/2010

... and other fascinating questions and answers about the cell's energy powerhouse.

  • slide 1 of 4

    What is the Origin of the Mitochondria?

    Mitochondria contain their own DNA and transcription and translation processes, separate from the nuclear DNA. Largely because of this it is widely suspected that they had an origin that is independent of other cellular organelles. According to the endosymbiotic theory, mitochondria originated from bacteria and way back in evolutionary time became incorporated into the cell cytoplasm.

    The evidence for this includes:

    • They contain their own DNA.
    • Are a similar size to bacteria.
    • Have a double set of membranes just like most bacteria.
    • Mitochondria DNA is circular, as is bacterial DNA.
    • Large similarities between mitochondrial ribosomal RNA and bacterial RNA.
    • Some enzymes and transport systems are similar to those in bacteria.

    The theory is more than a hundred years old but was given new life by American biologist Lynn Margulis in her 1981 work Symbiosis in Cell Evolution.

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    Why is the Mitochondria Important?

    Mitochondria are vitally important because they provide the energy for cells to carry out their metabolic functions. To do this they break down the glucose in our food into a substance known as ATP (adenosine triphospate). This process takes place in the matrix of each mitochondrion. Carbohydrates, proteins, and fats are converted into carbon dioxide and water, which generates energy that the cell can use.

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    How is the Mitochondria used in Forensic Science?

    Forensic scientists will use every tool they can to try and discover the perpetrator of a crime. Nuclear DNA fingerprinting is a well established field and now the use of mitochondrial DNA in forensics is enjoying a rapid growth spurt.

    • It does not degrade easily, unlike nuclear DNA, as it is sheltered well inside the cell.
    • It's been extracted from aged samples of hair, bone, and teeth, and is therefore useful when nuclear DNA is of poor quality.
    • Parts of the mitochondrial DNA sequence are highly polymorphic - known as hypervariable regions - useful for identification.
    • There is lots of mitochondrial DNA in each cell.

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    What are Differences Between Nuclear and Mitochondria DNA?

    The key differences between nuclear DNA and mitochondrial DNA are as follows:

    • Mitochondrial DNA is inherited solely down the maternal line. The mitochondrial genome is not a combination of the genomes of both parents.
    • Mitochondrial genome consists of 37 genes as opposed to the estimated 25,000-30,000 genes in the human nuclear genome.