Reparation: is this? Mechanisms of DNA repair

Reparation is a property of a living cell to fight various DNA damage. In the surrounding world, there are many factors that can cause irreversible changes in the living body. To maintain its integrity, avoid pathological and incompatible with life mutations, there must be a system of self-restoration. How is the integrity of the genetic material of the cell broken? Let's consider this issue in more detail. Also find out what are the restorative mechanisms of the body and how they work.

Disturbances in DNA

The molecule of deoxyribonucleic acid can be broken both during biosynthesis and under the influence of harmful substances. To negative factors, in particular, include temperature or physical forces of different origin. If destruction occurs, the cell starts the repair process. Thus begins the restoration of the original structure of the DNA molecule. Special enzyme complexes that are present inside the cells are responsible for the repair. With the inability of individual cells to carry out restoration, some diseases are associated. The science that studies the processes of reparation is biology. Within the discipline, a lot of experiments and experiments have been conducted, thanks to which the process of recovery becomes more understandable. It should be noted that DNA repair mechanisms are very interesting, as is the history of discovery and study of this phenomenon. What factors contribute to the beginning of recovery? In order for the process to start, it is necessary that the DNA stimulator reparation of tissues. What is this, we'll tell you in more detail below.

History of the discovery

This amazing phenomenon began to study the American scientist Kellner. The first significant discovery on the path of investigating reparation was the phenomenon of photoreactivation. By this term, Kellner called the effect of harm reduction from ultraviolet irradiation in the subsequent treatment of damaged cells by a bright flux of light from the visible spectrum.

"Light restoration"

Subsequently, the researches of Kelner got their logical continuation in the works of American biologists Setlaw, Rupert and some others. Thanks to the work of this group of scientists, it was reliably established that photoreactivation is a process that is triggered by a special substance - an enzyme catalyzing the cleavage of thymine dimers. They were, as it turned out, formed during the experiments under the influence of ultraviolet. In this case, bright visible light triggered the action of the enzyme, which contributed to the cleavage of dimers and the restoration of the initial state of damaged tissues. In this case we are talking about a light type of DNA repair. Let's define it more clearly. It can be said that light repair is the restoration under the influence of light of the original DNA structure after damage. However, this process is not the only one that contributes to the elimination of damage.

"Dark recovery"

Some time after the discovery of light was found dark repair. This phenomenon occurs without any exposure to visible light rays. This ability to recover was found during the study of the sensitivity of certain bacteria to ultraviolet rays and ionizing radiation. Dark DNA repair is the ability of cells to remove any pathogenic changes in deoxyribonucleic acid. But it should be said that this is no longer a photochemical process, unlike light restoration.

Mechanism of "dark" elimination of damage

Observations of bacteria showed that some time after the unicellular organism received a portion of ultraviolet, as a result of which some parts of DNA were damaged, the cell regulates its internal processes in a certain way. As a result, a modified piece of DNA is simply cut off from the general chain. The resulting gaps are again filled with the necessary material from the amino acids. In other words, the resynthesis of DNA is carried out. The discovery by scientists of such a phenomenon as dark tissue repair is another step in studying the amazing protective abilities of the animal and human organism.

How is the system of reparation

Experiments that revealed the mechanisms of recovery and the very existence of this ability were conducted with the help of unicellular organisms. But the processes of repair are inherent in living cells of animals and humans. Some people suffer from pigmentary xeroderma. This disease is caused by the lack of ability of cells to resynthesize damaged DNA. Xeroderma is inherited. What does the reparation system consist of? The four enzymes on which the repair process is kept are DNA-chelicase, -exonuclease, -polymerase and -ligase. The first of these compounds is able to recognize damage in the chain of a molecule of deoxyribonucleic acid. He not only recognizes, but also cuts the chain in the right place to remove the altered segment of the molecule. The elimination itself is carried out using DNA-exonuclease. Further, a new section of the molecule of deoxyribonucleic acid is synthesized from amino acids in order to completely replace the damaged segment. Well, the final chord of this most complicated biological procedure is performed with the help of DNA ligase enzyme. It is responsible for attaching the synthesized site to the damaged molecule. After all four enzymes have done their work, the DNA molecule is completely updated and all the damage remains in the past. That's how mechanisms work within the living cell.

Classification

At the moment, scientists identify the following types of repair systems. They are activated depending on various factors. These include:

1. Reactivation.
2. Recombination restoration.
3. Repair of heteroduplexes.
4. Excision repair.
5. Reuniting non-homologous ends of DNA molecules.

All single-celled organisms possess at least three enzyme systems. Each of them has the ability to carry out the restoration process. These systems include: direct, excisive and postreplicative. Prokaryotes are the three types of DNA repair. As for eukaryotes, they have at their disposal additional mechanisms called Miss-mathe and Sos-reparation. Biology has studied in detail all these types of self-healing of the genetic material of cells.

Structure of additional mechanisms

Direct reparation is the least complicated way to get rid of pathological changes in DNA. It is carried out by special enzymes. Thanks to them, the restoration of the structure of the DNA molecule takes place very quickly. As a rule, the process proceeds during one stage. One of the enzymes described above is O6-methylguanine-DNA methyltransferase. The excision repair system is a type of self-healing of deoxyribonucleic acid, which involves cutting out the altered amino acids and then replacing them with newly synthesized patches. This process is already carried out in several stages. In the course of post-replicative DNA repair, gaps in the structure of this molecule can be formed into a single chain. They are then closed with the help of RecA protein. The post-replicative repair system is unique in that there is no stage in its process of recognizing pathogenic changes.

Who is responsible for the recovery mechanism?

To date, scientists know that a simple being, like an E. coli, possesses no less than half a hundred genes that are responsible for the repair itself. Each gene performs certain functions. They include: recognition, removal, synthesis, attachment, identification of the effects of ultraviolet radiation and so on. Unfortunately, any genes, including those that are responsible for the repair processes in the cell, are mutated. If this happens, they trigger more frequent mutations in all cells of the body.

Than it is dangerous to damage DNA

Every day, the DNA of our cells is exposed to the danger of damage and pathological changes. This contributes to environmental factors such as ultraviolet radiation, food additives, chemicals, temperature changes, magnetic fields, numerous stresses that trigger certain processes in the body, and much more. If the DNA structure is broken, it can cause a heavy cell mutation, and may lead to cancer in the future. That is why the body has a set of measures designed to combat such damage. Even if the enzymes can not return the DNA to its original appearance, the repair system works to minimize damage.

Homologous recombination

Let's see what it is. Recombination is the exchange of genetic material in the process of rupture and connection of molecules of deoxyribonucleic acid. In the case when discontinuities occur in the DNA, the process of homologous recombination begins. In the course of it, fragments of two molecules are exchanged. Due to this, the original structure of deoxyribonucleic acid is accurately restored. In some cases, DNA penetration may occur. Thanks to the recombination process, it is possible to integrate these two dissimilar elements.

Mechanism of recovery and health of the body

Reparation is an indispensable condition for the normal functioning of the body. Being exposed daily and hourly to threats of DNA damage and mutations, the multicellular structure adapts and survives. This is also due to the established system of reparation. The lack of normal restorative capacity causes diseases, mutations and other abnormalities. These include various pathologies of development, oncology and even aging itself. Hereditary diseases due to reparation disorders can lead to severe malignant tumors and other anomalies of the body. Now some diseases caused by malfunctions of DNA repair systems have been identified. These are, for example, pathologies like Cocaine syndrome, xeroderma, non-colon cancer of the colon, trichodiodystrophy and some cancers.