A single symptom can be caused by many things whereas more than one syndrome can have similar causes. Eg. COX deficiency or Complex I/ Complex II deficiency come under general diagnosis of respiratory chain deficiencies.
Generally, the lack of energy synthesized by mitochondria leads to cell damage which could lead to a wide term of disorders under mitochondrial encephalomyalpathy; which affect specifically the respiratory chain (nothing to do with breathing).
Nuclear DNA mutations: Are less disastrous and easier to predict as most diseases like Leigh Syndrome ( defects caused in Complexes I and IV) are autosomal recessive which requires two copies of the gene for a phenotype to be seen. Thus less likely to be in effect.
Eg. Fatty Acid Oxidation Disorders (FAODs are autosomal reccessive)
Mitochondrial DNA mutations: Are more disastrous as they do not follow traditional Mendelian pattern of Inheritance where one set of genes come from the father and mother each. 100% of mitochondrial genes come from the maternal side only thus mutations are higher in ratio. Also, when a mutation occurs in mtDNA, heteroplasmy (where only some of the genes contain the mutation and not all) occurs, which gives us a very large range of diseases of varying severity that could arise in an individual. This is made even more unpredictable such that while only the mother passes on the mtDNA to the infant, it is not known how much of the maternal mtDNA is passed on during each reproduction.
Eg.
MERFF(Myoclonus epilepsy with ragged red fibers)
NARP (Neuropathy, ataxia and retinitis pigmentosa)
MELAS (Mitochondrial Encephalomyopathy, Lactic acidosis and strokelike episodes)
Spontaneous DNA mutations: Where both the mother and father do not have the disease and are usually caused by deletions.
Eg.
KSS(Kearns Sayre Syndrome which may cause eye problems, mental retardation)
PEO(Progressive External Opthalmolagia which affects eyes)
Pearson's Disease( Severe Anaemia and Pancreas malfunction)
Combination of nDNA + mtDNA mutations: Which are inherited by Mendalian Genetics patterens but also has mtDNA deletions.
Eg.
MNGIE(where a gene coding for thymidine phosphorylase is defunct in producing mitochondrial proteins)
Link- Mitochondrial Research Society http://www.mitoresearch.org/mitodiseases.html
Generally, the lack of energy synthesized by mitochondria leads to cell damage which could lead to a wide term of disorders under mitochondrial encephalomyalpathy; which affect specifically the respiratory chain (nothing to do with breathing).
Nuclear DNA mutations: Are less disastrous and easier to predict as most diseases like Leigh Syndrome ( defects caused in Complexes I and IV) are autosomal recessive which requires two copies of the gene for a phenotype to be seen. Thus less likely to be in effect.
Eg. Fatty Acid Oxidation Disorders (FAODs are autosomal reccessive)
Mitochondrial DNA mutations: Are more disastrous as they do not follow traditional Mendelian pattern of Inheritance where one set of genes come from the father and mother each. 100% of mitochondrial genes come from the maternal side only thus mutations are higher in ratio. Also, when a mutation occurs in mtDNA, heteroplasmy (where only some of the genes contain the mutation and not all) occurs, which gives us a very large range of diseases of varying severity that could arise in an individual. This is made even more unpredictable such that while only the mother passes on the mtDNA to the infant, it is not known how much of the maternal mtDNA is passed on during each reproduction.
Eg.
MERFF(Myoclonus epilepsy with ragged red fibers)
NARP (Neuropathy, ataxia and retinitis pigmentosa)
MELAS (Mitochondrial Encephalomyopathy, Lactic acidosis and strokelike episodes)
Spontaneous DNA mutations: Where both the mother and father do not have the disease and are usually caused by deletions.
Eg.
KSS(Kearns Sayre Syndrome which may cause eye problems, mental retardation)
PEO(Progressive External Opthalmolagia which affects eyes)
Pearson's Disease( Severe Anaemia and Pancreas malfunction)
Combination of nDNA + mtDNA mutations: Which are inherited by Mendalian Genetics patterens but also has mtDNA deletions.
Eg.
MNGIE(where a gene coding for thymidine phosphorylase is defunct in producing mitochondrial proteins)
Link- Mitochondrial Research Society http://www.mitoresearch.org/mitodiseases.html
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