Mitochondria are microscopic organelles that are scattered throughout the cytoplasm of all cells.
They contain a ring of DNA which is unique in that it is derived entirely from the mother. This DNA codes for a group of proteins known as the 'respiratory chain' whose role is to facilitate the conversion of glucose and oxygen to energy. Any abnormal mutation of this mtDNA is likely to effect most those processes such as insulin production, that are most energy dependent. There are many copies of each mitochondrial gene in each mtDNA ring and a mutation may not affect all of them. This characteristic, which is called 'heteroplasty' is supposed to account for the great clinical variability in mitochondrial diabetes.