Final answer:
Mitochondrial diseases like LHON, which are caused by mitochondrial DNA mutations, are always inherited maternally. Both male and female offspring are equally likely to inherit the disease, but only females can transmit it to the next generation. Symptoms vary due to differing levels of mitochondrial damage in cells.
Step-by-step explanation:
It is true that mitochondrial diseases such as LHON that are caused by mutations in mitochondrial DNA are always inherited from an offspring's mother. This is because only maternal mitochondria are passed down to offspring during reproduction. Mitochondrial DNA is distinct from nuclear DNA and is found within the mitochondria, which are inherited exclusively from the mother. Therefore, any mutations that occur within mitochondrial DNA can lead to mitochondrial diseases, which are transmitted maternally. This makes tracing genealogy through mitochondrial DNA particularly useful, as it can show maternal lineage.
Male and female offspring have the same likelihood of inheriting mitochondrial diseases if they contain mutations in mitochondrial DNA. However, only females can pass on these mitochondrial traits to their children. These diseases can have a variety of symptoms including muscle weakness, lack of coordination, stroke-like episodes, and loss of vision and hearing, which may manifest differently within the same family because of the varying extents of mitochondrial damage in different cells.