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In November, researchers from the University of California Los Angeles and the University of Alberta, Canada, reported in the journal Genome Research that deletion mutations and aberrant expression of mitochondrial DNA correlated with biological aging in humans and in rodents
What Are Mitochondria?
Mitochondria are the powerhouses of the cell, responsible for synthesizing the majority of adenosine triphosphate (ATP), the molecule that powers virtually all cellular functions.
Their unique structure and origins distinguish them as fascinating organelles.
Structure and Function
ATP Synthesis: Mitochondria use nutrients and oxygen to generate ATP via oxidative phosphorylation.
This energy is critical for processes such as muscle contraction, cell division, and signaling.
Dual Genomes: Mitochondria contain their own small, circular genome, called mitochondrial DNA (mtDNA).
This genome encodes only a small subset of the proteins and RNA molecules needed for mitochondrial function.
The majority of mitochondrial proteins are encoded by the nuclear genome, synthesized in the cytoplasm, and transported into mitochondria.
Evolutionary Origins
Mitochondria are believed to have originated from free-living bacteria that were absorbed by ancestral single-celled organisms over a billion years ago.
This event, known as endosymbiosis
Endosymbiosis, led to
Gene Transfer: Most of the bacteria's genes were incorporated into the nuclear genome, leaving behind a minimal genetic repertoire in mtDNA.
Dependency: Modern mitochondria cannot survive outside their host cells due to this genomic integration.
Inheritance
Mitochondria have a unique mode of inheritance:
Maternal Inheritance: Only the mitochondria from the mother's egg contribute to an offspring.
Mitochondria from the father's sperm are not passed on.
This means mtDNA is shared exclusively with maternal relatives, such as the children of a mother’s sister, but not with the children of a mother’s brother.
Nuclear vs. Mitochondrial Genomes
Nuclear Genome: Comprises 23 pairs of chromosomes, inherited equally from both parents (one chromosome of each pair from the mother and the other from the father).
A zygote (fertilized egg) contains two copies of each chromosome, which are then distributed across all cells in the body.
Mitochondrial Genome: Small, circular DNA that is maternally inherited.
Contains genes essential for mitochondrial energy production but depends heavily on nuclear DNA for its functions.
Mitochondria’s dual genomes and evolutionary origins provide a unique lens into cellular biology and inheritance, making them crucial to understanding energy production, aging, and genetic lineage.
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