Mitochondria contain multiple copies of mitochondrial DNA (mtDNA). When all copies are identical, the mitochondria is said to exist in “homoplasmy”. Sometimes, a copy of mtDNA has a variant (e.g. a C instead of a T). When variant mtDNA co-exists with wildtype mtDNA, the mitochondrion exists in a state known as “heteroplasmy”. If the level of heteroplasmy surpasses a certain threshold, the cell starts to exhibit phenotypic changes. In human disease this could mean the presentation of symptoms, for biopharmaceuticals this could mean a reduction in productivity.

Author: Alan Foley (ESR2)