Virtually every animal on Earth can thank its mother for the energy that fuels each cell.
Electricity is produced in parts of the cell known as mitochondria, an organelle made entirely from a genetic recipe built into the mother’s DNA.
The father’s mitochondrial DNA (mtDNA) plays no role. However, it is not clear at what point a father’s mitochondrial genes are significantly influenced, and a variety of studies support this idea. destruction of egg cytoplasmand significant editing of sperm it is forming.
A recent study that sequenced the genes of human sperm cells failed to detect intact mtDNA before fertilization, supporting early chopping.
Each sperm cell contains about 100 unique mitochondria, but the American and Spanish research team found no trace of male mtDNA within the mitochondria. Sperm also lacked transcription factors needed to maintain mtDNA.
The authors “conclude” write“Mature human sperm essentially lack mtDNA, consistent with maternal inheritance of the mitochondrial genome in mammals.”
Of course, male sex cells still provide nuclear DNA to offspring, and the human nuclear genome is billions of times larger than the mitochondrial genome.Still, mutations in the latter genome associated with various diseases and the aging processThis suggests that it is very important for health and function.
So why is only the mother’s mtDNA inherited?
One hypothesis This is related to the relatively high mutation rate of the mitochondrial genome compared to the nuclear genome. Each cell in the body contains many mitochondria, separated into daughter cells The parent cell will be split.
The way this division occurs is quite chaotic, all things considered, and means that the daughter cells may not get enough mitochondria to meet their needs. Making the few mitochondria they receive work harder only makes them more likely to split and mutate.
Because sperm cells rapidly churn up energy trying to reach a human egg for fertilization, if that mtDNA is present, it will likely accumulate a large number of mutations.
The egg cell, on the other hand, does not rely on its own mitochondria for energy. It saves those recipes for the future and instead siphons energy from the mitochondria of neighboring cells.
“Eggs transmit very good mtDNA, at least in part because they don’t use mitochondria as an energy source.” explain OHSU developmental biologist Shukhrat Mitalipov;
The finding does not explain why, in rare circumstances, scientists have found mtDNA transmission in some humans that appears as if it came from both the father and the mother. However, this may help experts better understand some fertility disorders that can be inherited through eggs and sperm.
In recent years, scientists have begun to find ways to target specific mutations in mitochondrial DNA to prevent them from being passed on to offspring.
In fact, around the world, several children have been born with DNA from three different people after their parents sought cutting-edge mitochondrial replacement therapy.
This incredibly unique baby, like any child, has nuclear DNA that comes from the fertilization of a sperm and egg, but her mitochondrial DNA comes from another female donor’s egg.
“Maternal inheritance of mtDNA is the primary paradigm guiding the existence and evolution of most species,” write the authors of the recent study. conclude“However, the molecular basis of this phenomenon and its benefits remain unclear.”
It’s incredible how little we know about such a fundamental part of life, where our genes come from.
This study natural genetics.