Explain the effect of heteroplasmy on the manifestation
of mitochondrial diseases.
When in a cell there is more than one type of organellar genome i.e. mitochondrial DNA or plastid DNA is present, such a condition is called heteroplasmy.
Mitochondrial disease is a condition in which due to genetic disorder in the mitochondrial DNA the mitochondria is unable to produce enough energy for the cell to function normally. Some of the examples of such conditions are; mitochondrial myopathy, diabetes mellitus, and deafness (DAD), Leigh syndrome, etc.
Heteroplasmy is the condition in which mitochondria have different types of genome in it. These multiple genomes may have a mutation in them. In normal condition, a few mutations do not cause any effect, however, when natural selections occur for such heteroplasmic cells and intracellular selection of genes occurs within the cells thus enabling the favoured genotype to thrive. In such conditions when these mutated genes and the cells containing the mutation survives, selected and thrives, their population starts growing which result in the significant expression of mutation replacing the original genotype.
In such a condition, the mitochondrial disease will proliferate and will occur. So, basically due to heteroplasmy the mutated genes get their opportunity to thrive and cause the mtDNA disease.
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