<s>[INST] context: Diseases associated with mitochondrial inheritance are rare and many of them affect the Neuromuscular System. Leber hereditary optic neuropathy is a prototype of this disorder. It is a neurodegenerative disease that Manifests itself as progressive bilateral loss of central vision. Visual impairment is first noted between ages 15 and 35, and it leads to blindness. Cardiac conduction defects & minor neurologic manifestations have also been seen in some families. Mitochondrial diseases
DNA in human may be found at two locations

Nuclear DNA in nucleus
Organelle DNA in the mitochondria

Mitochondrial DNA is the only non-chromosomal DNA in human cells. Mitochondrial DNA is always maternally inherited. Why is it so, let’s see:-
Mitochondrial and nuclear DNA are located in different places in the cell. During fertilization, the sperm and egg cell nuclei fuse to form an embryo. The egg cell is very large compared to the sperm, so although the cells’ nuclei fuse, the rest of the cell mass in the embryo comes from the egg only. Nuclear DNA is therefore co-inherited but the mitochondrial DNA, which is located outside of the nucleus, is always maternally inherited because all mitochondria in a foetus and later adult are derived from the Mitochondria in the mother’s egg.  All children from affected mother will inherit the disease but it will not be transmitted from an affected father to his children. [/INST] question: Mitochondrial chromosomal abnormality leads to - | options: A: Leber's hereditary optic neuropathy B: Angelman syndrome C: Prader-willi syndrome D: Myotonic dystrophy | answer: A </s>