Extranuclear Inheritance

Mitochondria are membrane bound organelles found in the cytoplasm of Eukaryotic Cells (Alberts et al., 2014), they can be circular or elliptical and have a double membrane (Silverthorn, 2012). ATP production occurs in them through the breakdown of carbohydrates in Oxidative Phosphorylation (Cooper, 2000). The amount of mitochondria in the cell depends on the energy requirement of the cell (Alberts et al., 2014), if the energy demand increases, the amount of mitochondria will increase (Silverthorn, 2012). Extranuclear inheritance exists due to the mitochondria having its own DNA (Hartl and Jones, 2003). Mitochondrial DNA (mtDNA) is more likely to mutate during replication as this process is not as reliable as nuclear DNA replication (Strachan and Read, 2010). Mutations in the mtDNA can lead to many disorders, the first one discovered was Leber Hereditary Optic Neuropathy (LHON). LHON is acute or sub-acute vision loss inherited from the mother and it usually affects males of young adulthood (Darley-Usmar and Schapira, 1994). Mitochondrial DNA is

However, it is known that these mutations in the mtDNA cause acute and sub-acute vision loss in the sufferers. It is a devastating condition due to the quick onset and also the lack of preventative methods. There are many unanswered questions with LHON such as why males are more affected and knowing whether the children of a sufferer will inherit the disease. More research is needed into heteroplasmic and homoplasmic mtDNA and their link to the inheritance of LHON. There are additional factors in the inheritance of LHON to just mutated mtDNA, which have an effect on whether the children of a mother with LHON will inherit it. To summarise LHON is a complex disorder of the mitochondria DNA, that has multiple additional factors which make it difficult to predict inheritance of the