Endosymbiotic Theory

The mitochondria is a cell organelle which plays an important role in the providing of cellular energy in eukaryotic cells. This occurs through the conversion of organic molecules into ATP through the process of aerobic oxidative phosphorylation. It is commonly accepted that the mitochondria is representative of an early prokaryote organism that established a symbiotic relationship with early eukaryotic cells (Snustad et. al 2010). This is known as endosymbiotic theory and means that the mitochondria contains its own genome. A genome is the genetic makeup of an individual, the mitochondrial genome consists of the DNA found in the mitochondrial matrix (Snustad et. al 2010). This codes for proteins and enzymes used within the mitochondria for

This is due to the fact the majority of the cytoplasm (containing mtDNA) is inherited from the maternal ova rather then the paternal sperm, meaning the mother’s mitochondrial disorder is passed onto the offspring (NSW Government, 2015). In the case of LHON disorder, symptoms normally begin to show around adulthood. This means that for Felicity, it will be hard to distinguish whether the mutation has been passed onto her offspring. Furthermore, LHON symptoms are seen much more frequently in men then women. In fact, males are four to five times more likely to be affected than females (Yu-Wai-Man et al. 2000). This is known as incomplete penetrance meaning that the genetic trait is only expressed in part of the population. Reasons for this are unknown, however it may signal that other genetic or environmental factors as well as the primary LHON mutation contribute to the death of optic nerve cells (Yu-Wai-Man et al. 2000). LHON mutations are mostly homoplasmic, with only 15% being heteroplasmic (Orssaud, 2003). This 15% of cases means that the proportion of mutated to non mutated mtDNA will determine whether LHON develops. This may as a result make it hard to predict whether the symptoms will show in an