MITOCHONDRIAL INHERITANCE
The hundreds of mitochondria in human cells have in each,
a few copies of circular DNA. Mutations involving these produce a small
number of genetic conditions.
CRITERIA
- Each mitochondrion contains a number of copies of DNA.
- The inheritance is matrilineal - Only mothers transmit
the condition to both sexes of children, but males do not transmit.
- Specific tissues like cardiac and striated muscle, organs
like the kidneys and systems like the central nervous system are rich in
mitochondria. As a result mitochondrial disorders are cardiomyopathies,
myopathies or neurological problems.
CLINICAL EXAMPLES
- Leber's Hereditary optic neuropathy shows optic atrophy,
occasional movement disorders and ECG abnormalities.
- Kearns - Sayre syndrome presents with progressive external
ophthalmoplegia, retinal pigment abnormalities, heart block and cerebellar
ataxia.
- MERFF or myoclonic epilepsy with ragged red fibres of
muscle biopsy is another disorder.
- MELAS shows a collection of features which include encephalomyopathy,
lactic acidosis and stroke-like episodes.