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The DNA is decreasing

For 1.5 billion years, the mitochondria - the powerhouse of the cell - have been sending DNA segments to the cell nucleus, and they merge with the DNA in the nucleus. A new study found that the contribution of the mitochondria to the DNA in the cell nucleus gradually decreases. This process is expected to reduce the incidence of some hereditary diseases

Mitochondrial structure. Illustration: depositphotos.com
Mitochondrial structure. Illustration: depositphotos.com

In the winter of 2021-2020, with the distribution of the first RNA vaccines for Corona, the vaccine opponents claimed that the RNA vaccine affects the DNA in cells, A claim that has no proof so far. RNA enters the cell nucleus, copies DNA from there, exits the nucleus into the cell cavity, reaches an organelle in the cell that produces proteins, and there gives instructions for protein production. But RNA cannot modify DNA. This RNA molecule, messenger RNA, is like a person copying a recipe from a cookbook onto a sheet of paper: he does not thereby change the original recipe in the cookbook itself. There are researchers whoGuess that the corona virus itself integrates into human DNA, but this claim has not yet been confirmed.

But there are viruses (retroviruses) that enter the cell nucleus and change the DNA. The best known of them is The HIV virus which causes the AIDS disease. The mitochondrion, the powerhouse of the cell, also enters the cell nucleus and changes the DNA. Thousands of mitochondria (plural of mitochondrion) are found in every cell in our body, and mitochondria also have DNA. Mitochondrial DNA has entered the cell nucleus ever since A mitochondrion merged with a cell about 1.5 billion years ago. The DNA of the mitochondria changes the DNA in the cell nucleus among plants and animals, including man.

An uninvited guest in the cell nucleus

Mitochondrial DNA was indeed present in human cells even before the evolutionary split of man from his common ancestor and the other great apes, six million years ago, but over 90 percent of the mitochondrial DNA that entered human cells did so after this evolutionary split, that is, in the six million years the last ones 

Mitochondrial DNA undergoes mutations at a higher rate than the DNA in the nucleus. This may damage the DNA in the nucleus. Mitochondrial DNA may interfere with the DNA in the cell nucleus to give instructions for the production of proteins, and this is how diseases arise, including diseases that result from a lack of proteins. But there are factors that make up for it. First, small units of mitochondrial DNA move into the cell nucleus more frequently than large units, which reduces the risk of serious mutations. Second, the entry of mitochondrial DNA into the human cell nucleus slows down, and may stop. In a study published in October 2022 inNature, researchers at Queen Mary University of London his age that during the last six million years, the proportion of mitochondrial DNA that has entered the DNA in the nucleus of the human cell is decreasing. In addition, since our ancestor split into several species of apes, mitochondrial DNA undergoes mutations that remove pieces of DNA from it. Mitochondrial DNA that undergoes diminishing mutations survives longer than other mitochondrial DNA mutations, mutations in which the size of the DNA is preserved and thus smaller and smaller DNA is passed on to the next generation. This hypothesis regarding a reduction in the amount of mitochondrial DNA is similar to the hypothesisShrinkage of Y chromosome, the chromosome that determines male sex in mammals, including humans, although there are division on the degree of shrinkage and the rate of its occurrence. 

Reduction without demolition

The mitochondrial DNA fuses with the DNA in the nucleus. How does he do this without destroying the DNA in the nucleus? First, a genetic repair mechanism operates on the mitochondrial DNA the facility Harmful mutations, similar to the one that acts on the DNA in the nucleus. This mechanism reduces the likelihood of developing mutations, including those that may cause cancer. This is how the carrier of the mutations survives and inherits them to the next generation. "survives" and not "survives", because mitochondrial DNA Inherited only through the egg, not through the seed, i.e. only through the mother, not through the father. 

Second, once in every 4,000 births, mitochondrial DNA passes into the cell nucleus, but it is possible that mutations in mitochondrial DNA occur in neutral DNA regions, which do not participate in protein coding. In the past, such neutral DNA was called "junk DNA". Today the explanation is that most of this DNA plays other roles, among others bGene control

Third, it is possible that the proteins encoded by the mitochondrial DNA became redundant during evolution and therefore their non-production does not harm the organism. Fourth, it is possible that other genes back up the mitochondrial genes in protein production, and thus mutations that reduce the amount of mitochondrial DNA do not harm the carrier.

As the amount of mitochondrial DNA decreases in the DNA in the nucleus, the chance of development decreases Diseases associated with impaired protein production such as Alzheimer's, cystic fibrosis and hemophilia. Perhaps this way the incidence of these diseases will decrease during the ongoing evolution of the human race. But since this change occurs at an evolutionary rate, it is unlikely to happen within a generation or two, nor within a few hundred years. Our grandchildren-great-grandchildren may get to see this change. The current generation can only recognize the expected trend following the genetic road signs that the mitochondria leave us.

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