The main function of mitochondria is energy metabolism. Mitochondrial disorders are most likely to affect tissues such as the brain, the eye, skeletal and cardiac muscle which all have high energy requirements for normal function.
The main store of DNA is in the cell nucleus, however mitochondria also contain DNA but are found in the cell cytoplasm. The genes on this mitochondrial DNA produce a small number of mitochondrial proteins. These genes are unique because each person inherits them only from their mother. The egg (unlike sperm) contains cytoplasm as well as a nucleus and this means that although both males and females may be affected by mitochondrial diseases, transmission is only by affected women.
Diseases affecting mitochondrial function may be controlled by nuclear gene mutation and follow mendelian inheritance, or may result from mutations within the mitochondrial DNA. Complex genetic testing is required to determining which mechanism is operating.
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