Mitochondria are the cellular organelles that are responsible for the production of energy. They are maternally inherited because they are supplied by the egg at fertilization. Mitochondria contain their own their own DNA, including 39 genes that are susceptible to mutations at a rate 10-20 times higher than nuclear DNA. In addition, there are a number of nuclear genes that are important for mitochondrial function. The inheritance pattern for mitochondrial disorders includes traditional Mendelian inheritance patterns (autosomal dominant, autosomal recessive, X-linked recessive), as well as mitochondrial inheritance patterns. In general, mitochondrial disorders involve multiple organ systems and can present at any age.
Important concepts of mitochondrial inheritance:
- Maternal inheritance
- Males and females are equally affected
- Disease phenotype is determined by:
- Type of mutation
- Prevalence of abnormal mitochondria
- Heteroplasmy - There is a mixture of normal and mutant mitochondria within each cell.
- Homoplasmy - The mitochondria within a cell are the same (all normal or all mutant).
- Organ system that is affected
An illustration of mitochondrial inheritance can be found at: Mitochondrial Inheritance patterns - Genetics Home Reference