By CRG Staff

from GeneWatch 27-3 | Sept-Nov 2014

The mitochondria are semiautonomous organelles with their own genomes and transcriptional machinery residing in the cytoplasm of eukaryotic cells. Mitochondrial cells contain 37 genes that encode 13 proteins, 22 transfer RNAs and 2 ribosomal RNAs. In contrast, the nuclear genome consists of about 20,000 genes. Mitochondria are the powerhouses of cells - they store and transmit chemical energy. They multiply when the energy needs of the cell increases. The primary function of the mitochondria is the generation of the molecule ATP (adenosine triphosphate) from food sources. ATP is often referred to as the energy currency of life.

Mitochondrial diseases are a group of disorders that can cause debilitating, chronic illness. They are the result of either inherited or spontaneous mutations in mitochondrial DNA (mtDNA) or nuclear DNA (nDNA), which lead to altered functions of the proteins or RNA molecules that normally reside in the mitochondrial cells. These mutations can be present at birth or develop later in life and cause mild to severe physical, developmental, and mental disabilities. When mitochondria aren't working properly, they can disrupt function in almost any of the body's organs. Depending on which cells are affected, symptoms may include loss of motor control, muscle weakness and pain, gastro-intestinal disorders and swallowing difficulties, poor growth, cardiac disease, liver disease, diabetes, respiratory complications, seizures, visual/hearing problems, lactic acidosis, developmental delays and susceptibility to infection.

Mitochondrial diseases can be difficult to diagnose. At least one in 8,500 of the population carries a pathogenic mtDNA mutation, while it is estimated that up to 4,000 children per year in the US are born with a type of mitochondrial disease. They are progressive and incurable, though some treatments are available depending on the case.


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