Question

leber's hereditary optic neuropathy (lhon) is a disease caused by a mutation in mitochondrial dna that usually produces acute loss of vision, resulting in complete blindness in young adulthood. bill has a severe case of lhon. his mother, however, has only a mild case of the disease. what is the most likely explanation for the fact that bill is severely affected but his mother is only mildly affected?

Answer 1

The severity difference in LHON symptoms between Bill and his mother is likely due to the different levels of mitochondrial DNA mutations present in their cells, known as heteroplasmy.

Step-by-step explanation:

Leber's Hereditary Optic Neuropathy (LHON) is a condition caused by mutations in mitochondrial DNA, which can produce acute vision loss leading to blindness, often in young adulthood. The severity of LHON symptoms can vary significantly, even within the same family.

This phenotypic variability may be due to different levels of heteroplasmy, which is the existence of both normal and mutated mitochondrial DNA within the same cell. It is likely that Bill has a higher percentage of mutated mitochondrial DNA compared to his mother, who has a milder case, possibly due to a lower level of heteroplasmy.

The mitochondrial inheritance pattern is unique because these organelles are typically inherited exclusively from the mother; therefore, all offspring of an affected mother may inherit the mutation, but only those with a higher proportion of defective mitochondria will express severe symptoms.