In the word mutation, many people probably think of abominably deformed creatures from horror movies rather than biology. Mutations play an important role in biology everywhere: for the evolution, the emergence of new species, the emergence of new creatures and, finally, the emergence of many diseases. The mutation, however, takes place on a much smaller scale than in the movie: as a tiny change in a tiny spot of our genome in just a single cell of our body. Such mutations happen thousands of times in our body. For a mutation to result in an externally visible change at the end, therefore, many coincidences really have to come together.

What is mutation?

By definition, a mutation is a permanent change in our genome, which is passed from the once mutated cell in the context of cell division to their daughter cells.

By definition, a mutation is a permanent change in our genome, which is passed from the once mutated cell in the context of cell division to their daughter cells.

If this mutation occurs in a sperm or egg cell of our germ line, the mutation is possibly passed on to the offspring and one speaks of a germline mutation - this results in biological diversity and in the long term evolution, in the worst case but also hereditary diseases.

If the mutation occurs in every other cell of the body, it is called a somatic mutation - in most cases this cell is dysfunctional and rejected by the immune system, in the worst case it dances out of line, divides uncontrollably and becomes a tumor.

Functions & Tasks

After the cause, one can distinguish spontaneous and induced mutations. Spontaneous mutations arise without external cause and almost constantly in our body.

In every second countless cell divisions take place in the human organism, each time the DNA, in other words our genetic material, has to be doubled and distributed to the two resulting daughter cells - clearly that something goes wrong! Furthermore, bases from the DNA can spontaneously disintegrate chemically and suddenly one of the bases forms another, which suddenly gives completely different information for the reading mechanisms.

Induced mutations are caused by external influence and there are many suspects: The mutagenic effect is for example protected for radiation and many so-called carcinogenic substances such as nitrosamines from cured meat or benzpyrenes from cigarette smoke. It is unlikely that such induced mutations in this world can be completely prevented, but a whole series of pollutants and risk factors are now known, the avoidance of which can reduce the risk of a mutation to a minimal residual:

Do not smoke, do not eat burnt meat, cream before sunbathing, make x-rays only when absolutely necessary, protect against radiation at the workplace, etc. - this will avoid much of the cell-level mutation.

In the remaining cases, such a mutation is then not bad: A large part of our DNA is already without significance for the transmission of genetic information - a mutation there so does not change the pattern of the proteins read. But once a site mutates genetic information that codes for an important protein in the cell metabolism, there are several protective barriers: Among other things patrolling constantly proteins as "guardian of the genome" in our cell, which recognize mutations and - depending on the extent - either directly repair or, in case of irreparability, simply initiate controlled cell death.

The immune system then simply clears these cells and new ones come after. If this protective mechanism fails and the DNA is finally read incorrectly, in most cases nonsense comes out, the cell becomes functionless and stays with its nonsense protein until it dies. Only if a mutation happens to create something "meaningful", ie something that always works, at a decisive point, this sometimes has major biological effects.

Diseases, complaints & disorders

If the mutant cell is a germ cell, for example, a sperm, and if this sperm should eventually prevail in the race for the fertilization of an egg, every smallest mutation in the genetic material can have major consequences: another hair color, one One centimeter more height, different intelligence, different interests, another person - everything is conceivable.

In this way, evolution has occasionally just accidentally tried certain human, animal and plant properties, and if they prove to be good, they prevail. Also, each child is not just the sum of mother and father, but at the same time also the product of small mutations, which in turn give rise to completely new properties and keep the genome surprisingly interesting, even within the family line.

In addition, today's medicine but also a lot of defined mutations on certain genes are known that differ so far from the human "normal" that they can be described as hereditary diseases: In CF, for example, a single gene on chromosome 7 minimal change - with maximum Effects on the quality of life and life expectancy of those affected. In Down's syndrome, on the other hand, the number of chromosomes is mutated - there are three instead of two copies of the 21st chromosome, which is why the disease is also called trisomy 21.

There are many more examples of more serious hereditary diseases, which may spread to the offspring of the patient. Some of them are inherited only recessively: that is, they are mostly covered by a healthy partner chromosome and only appear as an illness when the partner chromosome is also mutated. Genetic disorders in the larger family may be indicative of the presence of such hidden mutations and justify visiting the human geneticist before procreating a child.

In the meantime, somatic mutations are more relevant to those who are not newborns or parents-to-be. If any body cell mutates (which, as I said, happens all the time), it loses control of its cell division with a bit of bad luck. This is how cancer develops. This mutation can not be undone either and is passed on to all daughter cells, so that they too want to continue to divide infinitely without taking any necessities or external influences from the rest of the body into consideration.

The tumor grows and grows - and hopefully will be discovered quickly enough, as long as it can be surgically removed without major collateral damage and has not yet spread any metastases in the body.

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