People from the very beginning of their existence are engaged in knowledge of themselves and the world around them. And often research activities leads to the fact that people intentionally interfere in the usual processes, thereby disrupting the course of events and introducing obvious changes that affect not only the surrounding nature, but also the person.
Definition
Mutagenesis is the process of changes in the structure of DNA, as a result of which a mutation occurs in an organism.
There are two types of mutagenesis: artificial (induced) and natural (spontaneous).
Discovery history
In 1899, the Russian scientist Korzhinsky provided a scientific explanation for mutagenesis. In 1900, the geneticist Fries continued to study the phenomenon, and it was this scientist who gave the current definition of mutagenesis.
These two scientists deduced the following provisions of his theory:
- All mutation processes are sudden, like intermittent changes in traits.
- The new obtained forms are stable.
- Mutations do not "build" successive series, do not accumulate near the average type. This significantly distinguishes mutational changes from hereditary ones.
- Similar mutations may appear intermittently.
- Depending on the number of individuals studied, the probability of detecting a mutation increases.
- Mutations are both harmful and beneficial.
Why Mutations Occur
Most often, mutagenesis occurs when errors are made when doubling and restoring DNA chains, when there is a violation in the divergence of chromosomes to the poles during meiosis.
In general, in every cell there is a constant restoration of broken DNA chains. However, if DNA integrity is not restored, then all errors in the genetic code will accumulate, which will eventually lead to the mutation process.
Spontaneous mutagenesis
It occurs under natural conditions of development, when no mutagens act from the outside.
What could be the reasons for the appearance of this type of it:
- Exogenous (or external): radiation, extremely low or high temperatures.
- Endogenous (or internal). These include metabolites that are suddenly formed in the body, which awaken the formation
So, for example, in the zones of the Arctic cold, the vegetation has a polyploid form. This depends on the fact that a number of genomic mutations are formed in plants during the growing season at abnormally low temperatures.
For a long time, scientists believed that cosmic waves and natural radiation were factors in the occurrence of natural mutagenesis. However, in the course of the studies carried out, it was found that only a small proportion of spontaneous mutagenesis is formed under the influence of radiation.
Found to be caused by local small deviations thermal motion particles.
induced
Artificial type mutagenesis is the process of creating artificial mutations in order to obtain the necessary material.
For example, in plant breeding, scientists use which transform the original genotype. In the course of this, modified plant species are obtained with new features and forms that are not found in their original species.
Therefore, we can say that induced mutagenesis in breeding plays an important role in obtaining new varieties.
Methods of spontaneous mutagenesis
Its mechanism looks like a violation of a DNA fragment. If it was carried out with errors, then the formation of a mutation is inevitable. If the violation occurred in an unimportant DNA region, or vice versa, in meaningful fragment, then the mutation will appear, but once and will not appear again.
Mutagens: physical and chemical
Mutagens are phenomena that cause mutational changes in an organism. By the nature of their origin, they are all divided into physical and chemical.
Physical mutagens include:
- Ionizing radiation.
- Temperature.
- Humidity.
Their methods of influence are as follows:
- Destruction of the integral structure of chromosomes and genes.
- The release of free-type radicals, which begin to interact with DNA.
- Violation of the integrity of the filaments of the chromatin spindle division.
- The emergence of dimers - formations of single complexes of pyrimidine bases of one DNA strand.
Chemical mutagens are as follows:
- Chemical substances of organic and inorganic nature.
- Substances of a synthetic nature that have not been found in nature before.
- Natural substances after factory processing, such as coal and oil.
- Some medicines, narcotic substances, some types of antibiotics.
The mechanism of chemical mutagens is as follows:
- Alkylation of DNA nucleotide complexes.
- Substitution of nitrogenous bases for bases of a similar nature.
- Slowing down the synthesis of nucleic acid precursors.
Is there a benefit to mutagenesis?
So, we can say with confidence that mutagenesis is a phenomenon that can affect the state of the body.
If the mutagen affects an “insignificant” fragment of DNA, then, in fact, the body will not undergo any changes. Mutations will exist in the "memory" of DNA and be inherited, and over time they may disappear altogether.
But if the mutagenesis factors affect a significant DNA fragment, as a result of which the standard amino acid sequence is violated, this will lead to irreversible changes in the body. And if a mutation is detected in the vast majority of individuals of a certain species, then in the future this will lead to significant changes. characteristic features kind.
Since mutagenesis is a violation of the normal integrity of DNA, mutations can harm the body.
The overwhelming number of mutations can reduce the vital activity of organisms and provoke the appearance of serious diseases.
Those consequences of mutagenesis that are formed in somatic cells are not transmitted with the genetic material to the next generation. But as a result of mitotic division, when new cells form tissue, tumor seals can form.
Mutations that affect germ cells can be passed on to the next generation.
A specific example: a mutation that leads to the appearance of shortened wings in one of the representatives of an insect will subsequently appear in the rest of its species, and if these insects live in a calm area, then it will be difficult for them to move. In this case, we will talk about an acquired disease or even deformity.
But if strong winds begin to blow in such an area, then the original species of insects with long wings will suffer inconvenience, while short-winged ones, on the contrary, will have advantages.
Thus, it can be said that mutations can generate a new species of organisms by changing the genomic structure of an existing species.
Scientists... must feel responsible for all the consequences of their discoveries...
IN AND. Vernadsky
The main goal of genetic monitoring is to identify the volume and content of the genetic load of each generation of human populations, as well as quantitative criteria for the consequences of mutagenesis (quantitative risk assessments - KOR - and relative genetic efficiency - RGE). The genetic load is a part of the hereditary variability of a population, which determines the appearance of individuals that die selectively in the process of natural selection.
History of discovery and study of mutations
The concept and the term "mutation" itself appeared in ancient times, in the II century. AD, during the reign of the Roman emperor Hadrian. Mail, in our understanding, did not exist then. Letters to different parts of the state were delivered by messengers - horse and foot, who rested and changed horses in roadside taverns. In Latin, change mutatio.
The systematic study of mutations in organisms began only in 1880 with the work of Hugo de Vries. But long before that, many more or less obvious cases of mutations had already been noted. In 1590, a large celandine plant grew in one of the gardens of Heidelberg ( Chelidonium majus) with lanceolate leaves. AT late XVII in. in New England (in the state of Massachusetts), a sheep with very short curved legs and a long body appeared, which became the ancestor of the Ancon sheep breed. These sheep could not even jump over low hedges or stone fences of pastures, so they could not damage the fields. Shepherds, dogs, high fences are not needed for such sheep. The economic benefits of breeding the Ancon breed are obvious. Then came the polled cow, the benefits of keeping which need no explanation.
C. Darwin was well aware of cases of such sudden changes. For them, he proposed the term "single changes", or "sports".
The term "mutation" in its modern sound was proposed by Hugh de Vries in the classic work "The Mutation Theory" (1890). The main object of his research was the evening primrose plant. Simultaneously with the Russian researcher S.I. Korzhinsky, he discovered among the evening primroses one specimen, significantly larger than the others. For five years, the scientist followed the development of this evening primrose. All descendants of this altered (mutant) organism retained "gigantism" - they were tall, with a large number of leaves and stems. De Vries found other mutant forms of evening primrose - short in stature, more delicate in structure, some were very weak, while others were very strong. The fruits of plants also differed: in some plants they were similar to the fruits of the mother species, in others they were shorter and thicker, in others they were thinner and longer.
De Vries surprisingly correctly formulated the concept of mutation: the phenomenon of an abrupt, discontinuous change in a hereditary trait. S.I. Korzhinsky, having reviewed a huge amount of archival botanical materials, came to a similar conclusion: “the emergence of new forms is a phenomenon common to the whole world of living beings, and hereditary changes always occur in leaps and not gradually.” The modern definition includes the concepts of molecular biology: a mutation is a sudden qualitative change in the structure of DNA at one locus (genetic) or a change in the number or microstructure of chromosomes (chromosomal).
The study of mutations is carried out on models of experimentally induced mutations, and, in addition, cases of congenital anomalies in children, genetic diseases, etc. are carefully studied.
Attempts to artificially cause mutations were made by L. Pasteur, who designed a special apparatus with which he hoped to disrupt heredity. Other researchers have tried to cause mutations using chemical compounds, sudden changes in temperature. Unfortunately, these works not only did not receive recognition, but were also of no importance, since at that time there was still no method to determine the frequency of mutations, to distinguish true mutations from simple splitting of characters.
Only in 1925 did our compatriots G.A. Nadson and G.S. Filippov were successful: in their experiments, irradiation of yeast with X-rays significantly increased the frequency of mutations. Two years later, in 1927, a similar result was obtained by the American scientist G. Meller, irradiating the fruit fly Drosophila, a classic object genetic research. In the same year, the Fifth International Genetic Congress was held in Berlin, at which the message of G. Meller became a sensation: X-rays caused a 150-fold increase in the frequency of mutations.
After 9 years, the American scientist T. Morgan continued to study radiation mutagenesis in Drosophila. Soon, more than 500 radiation-induced mutations were identified by the joint efforts of geneticists around the world. In 1946, for his work in this area, G. Meller was awarded Nobel Prize. Thus, it was shown that ionizing radiation has a strong mutagenic effect.
Quite a bit of time passed, and in 1955-1958. scientists of our country, headed by Academician N.P. Dubinin, evaluating the genetic effect of radiation, found that a dose of 10 rad (10 rem) doubles the frequency of mutations in human fibroblast cells
(in culture). This value was adopted as the maximum allowable dose by the Scientific Committee on Radiation and then approved by the UN General Assembly (Geneva).
Studies of the mutagenic effect of chemical compounds were also started quite a long time ago. The first experimental work was carried out by our compatriots - famous scientists V.V. Sakharov and M.E. Lobashev in 1934. They showed that the action of chemical compounds causes an increase in the frequency of mutations in buckwheat cells. Later I.A. Rappoport in the USSR and S. Auerbach in Great Britain discovered powerful chemical mutagens and named them supermutagens.
In 1946 I.A. Rappoport found that under the action of formaldehyde in a sublethal dose on Drosophila larvae, 47 lethal sex-linked mutations (per 794 chromosomes) arose. In the control group, only one mutation per 833 chromosomes was found.
S. Auerbach and D. Robson showed that under the influence of sulfur and nitrogen analogues of mustard gas (mustard gas) on Drosophila, the frequency of sex-linked mutations increased from 0.2% (control) to 24%. Subsequently, these authors found that these substances cause both rearrangements of chromosomes and all kinds of direct and reverse point mutations. Comparisons of the effects of chemicals (mustard gas, formaldehyde and urethane) with radiation exposure conducted by British scientists did not reveal fundamental differences in the nature of the induced changes: chemical compounds, like radiation exposure, induce both gene and chromosomal mutations.
Subsequently, it was shown that a large number of artificially synthesized substances are mutagens and carcinogens. This discovery led to the conclusion made in the 70s. last century professor of the department medical genetics University of Wisconsin Crewe: “There is every reason to be concerned that some chemical substances can be as dangerous as radiation, and even more.”
In the 1960s the first attempt was made to classify chemical mutagens according to their structure and action.
Spontaneous and induced mutagenesis in humans under the action of environmental mutagens
Spontaneous mutational process in the DNA of chromosomes of sex and somatic cells of humans, animals, plants and microorganisms has occurred throughout the history of life on Earth. As a result, some of the zygotes died at the fetal stage, and some of the newborns appeared with defects.
To be continued
In anthropology, a number of hypotheses have been put forward that try to solve this problem, assuming that man became a man thanks to: life in water; mutations in the brain cells of hominids, caused by hard radiation from a supernova explosion, or geo inversions magnetic field; a mutant in the hominid community appeared as a result of heat stress. Let us consider these hypotheses in the order presented.
The hypothesis of the Swedish researcher J. Lindblad is very original. According to her, the South American Indians living in the rainforest are the most ancient people on Earth, and the predecessor of man was the “hairless monkey”, or “ixpitek”, leading an aquatic lifestyle. It is the reduced hairiness, upright posture, long hair on the head, emotionality and sexuality inherent only in humans that are due to the peculiarities of the lifestyle of the aquatic hominid (he spent most of the day on the shore). “As always, when a new way of life increases the percentage of survival,” writes J. Lindblad, “mutational changes in hereditary structures entail adaptation to the aquatic environment. Here it is expressed in a decrease in body hairiness and the development of a layer of subcutaneous fat. However, the hair on the head is long, an important factor for the survival of the young. In the first years of life, cubs have a particularly powerful layer of subcutaneous fat. The legs of the ixpitec are longer than the arms, the big toes are not opposed and point forward. The posture when walking is more straight - perhaps the same as ours. In other words, ixpitek has quite human species at least at a distance. Further development of the skull and brain led to the appearance of a modern type of man. Within the framework of the recent times this direction scientific research, as "cosmic catastrophism", a hypothesis has been put forward about the emergence modern man due to the explosion of a nearby supernova. It was recorded that a very surprising circumstance is that the outbreak of a nearby supernova in our Galaxy of a star in time (occurring once in 100 million years) approximately corresponds to the age of the oldest remains of Homo sapiens (35-60 thousand years ago). In addition, some of the anthropologists believe that the appearance of modern man is due to mutation. And the pulses of gamma and x-ray radiation from a supernova explosion are known to be accompanied by a short-term increase in the number of mutations. In this case, the intensity on the Earth's surface sharply increases ultraviolet radiation, which is a mutagenic agent, which, in turn, initiates the appearance of other mutagens. Ultimately, we can say that the hard radiation generated by the supernova explosion could cause irreversible changes in brain cells, which led to the formation of intelligent mutants of the species? Homo sapiens. At least with supernova explosions modern science connects: education solar system, the origin of life and, possibly, the origin of the modern type of man with his civilization.
Another hypothesis comes from the fact that modern man is a mutant that arose as a result of the inversion of the earth's magnetic field. It has been established that the terrestrial magnetic field, which mainly delays cosmic radiation, sometimes weakens for reasons unknown so far; then there is a change in the magnetic poles, i.e. geomagnetic inversion. During such reversals, the degree of cosmic radiation on our planet will increase dramatically. Exploring the history of the Earth, paleomagnetologists came to the conclusion that over the past 3 million years magnetic poles The lands changed places four times. Some of the discovered remains primitive people belong to the epoch of the fourth geomagnetic reversal. Such an unusual combination of circumstances leads to the idea of the possible influence of cosmic radiation on the appearance of man. This hypothesis is strengthened by the following fact: a person appeared at a time and in those places in which power radioactive radiation turned out to be the most favorable for the change of great apes. It was these conditions that arose about 3 million years ago in South and East Africa - during the period of separation of man from the animal world. According to geologists, deposits of radioactive ores were exposed in this region due to strong earthquakes. This, in turn, caused a mutation in some monkey species that was most predisposed to changing genetic traits. It is possible that about 3 million years ago, prolonged exposure to radioactive radiation so profoundly changed Australopithecus that he became able to perform the actions necessary for his safety and food supply. In accordance with this hypothesis, Pithecanthropus appeared about 700 thousand years ago, when the second change in the geomagnetic poles of the Earth occurred (250 thousand years ago), Neanderthal appeared, while the appearance of modern man falls on the fourth geomagnetic inversion. This approach is quite legitimate, because the role of the geomagnetic field in the life of organisms, including humans, is known.
The following hypothesis says that we all belong to the same subspecies of “reasonable man” and are descended from one foremother and one forefather, a very specific man and woman (more precisely, as it is now believed, a group of about 20 men and 20 women), whose descendants we are , now living people. More strictly, as we shall see, they should be called genetic Adam and Eve. Their real existence is recognized by the scientific majority, but some scientists still doubt this. Adam and Eve lived approximately 150-200 thousand years ago in Africa, and they still cannot be attributed to Homo sapiens, but rather to Homo erectus. They lived in different places and at different times. Naturally, they were not alone - around them and at the same time with them lived tens of thousands of other quite the same people. Certainly some of them are also our ancestors. The difference is that these others were the ancestors of some of us, maybe even many of us, but, fundamentally, not all of us. The concept of genetic Adam and Eve suggests that these two "humans" are the direct ancestors of ALL people now living on Earth.
This is the general hypothetical-theoretical situation in the development of the problem of anthropogenesis today. Not everything in it is fully clarified and explained, not everything scientists agree with each other. But there is nothing surprising in this, because we are dealing with the crown of the creation of nature - man. It is important to emphasize the following: in science it can be considered proven that man is a product of the natural development of nature. It has its roots in the biosphere of the Earth and is its legitimate child.
Concepts of ethnology
Ethnology - (from the Greek ethnos - nation, people, logic) ethnology, a science that studies the everyday and cultural characteristics of the peoples of the world, the problems of origin (ethnogenesis), settlement (ethnography) and cultural and historical relationships between peoples. It took shape as a science in the 19th century with the emergence of the evolutionary school, the appearance of research by L. G. Morgan and the book by F. Engels “The Origin of the Family, Private Property and the State” (1884), which formulated the foundations of the doctrine of the primitive communal system. Great merits in the development of ethnology in Russia belong to N. N. Miklukho-Maclay, M. M. Kovalevsky, and D. N. Anuchin. Ethnology is an emerging science. The need for it arose only in the second half of the 20th century, when it became clear that the simple accumulation of ethnographic collections and observations threatens that science, which does not pose problems, will turn into meaningless collecting. And so social science and ethnology arose before our eyes - two disciplines that are interested in one, at first glance, subject - a person, but in completely different aspects. And this is natural. Each person is simultaneously a member of society and a member of an ethnic group, and this is far from the same thing.
Mankind, which has existed on Earth for a very short time, some 30-50 thousand years, nevertheless, made upheavals on its surface, which V. I. Vernadsky equated with small-scale geological upheavals. This problem is relevant for our generation, and it will become especially relevant for our descendants. Man as a biological being belongs to the genus Homo. This genus, when it appeared on Earth, was characterized by a rather large diversity of species. This also applies to those types of Homo, which we, strictly speaking, have no right to consider as people, namely: Pithecanthropes and Neanderthals. Ethnicity in humans is the same as prides in lions, packs in wolves, herds in ungulates. It's a form of existence species Homo sapiens and its individuals, which differs both from social formations, and from purely biological characteristics, which are races.
In the number of races, the opinions of anthropologists disagree - four or six. And by appearance, and in terms of psychophysical characteristics, representatives of different races are very different from each other. Race is a relatively stable biological characteristic of the species of people, but it is by no means a form of their hostel, a way of their life together. Races differ in pure outward signs that can be determined anatomically. Just as an ethnos does not coincide with a race, it does not coincide with another biological grouping of individuals - a population. Population - the sum of individuals living in the same area and randomly interbreeding with each other. There are always marriage restrictions in an ethnic group. Two ethnic groups can coexist on the same territory for centuries and millennia. They can mutually destroy each other or one will destroy the other. This means that ethnos is not a biological phenomenon, just as it is not a social one. “That is why I propose to consider ethnos as a geographical phenomenon,” wrote the Russian ethnologist S. Lurie, “always associated with the enclosing landscape that feeds the adapted ethnos.” And since the landscapes of the Earth are diverse, ethnic groups are also diverse.
The dependence of a person on the nature around him, more precisely, on the geographical environment, has never been disputed, although the degree of this dependence was assessed differently by different scientists. But, in any case, the economic life of the peoples inhabiting and inhabiting the Earth is closely connected with the landscapes and climate of the inhabited territories. The rise and fall of the economy of ancient eras is rather difficult to trace because of the inferiority of information obtained from primary sources. But there is an indicator - military power.
On the significance of geographical conditions, for example, relief for military history, has been said for a long time, one might say, always. However, dwelling on such a clear problem in the 20th century is inappropriate, because history now poses much deeper tasks than before, and geography has moved away from a simple description of the curiosities of our planet and has gained opportunities that were inaccessible to our ancestors.
So the question is different. Not only how does the geographical environment affect people, but also to what extent people themselves are integral part that shell of the Earth, which is now called the biosphere. Which patterns of human life are influenced by the geographic environment and which ones are not affected? This formulation of the question requires analysis. Speaking of the history of mankind, they usually have in mind the social form of the movement of history, that is, the progressive development of mankind as a whole in a spiral. This movement is spontaneous and because of this alone it cannot be a function of any external causes whatsoever. On this side of history, neither geographical nor biological effects cannot influence. So what do they affect? on organisms, including humans. This conclusion was made already in 1922 by the outstanding Russian physiogeographer Lev Berg for all organisms, including humans: “The geographical landscape affects organisms, forcing all individuals to vary in a certain direction, as far as the organization of the species allows. Tundra, forest, steppe, desert, mountains, aquatic environment, life on islands, etc. - all this leaves a special imprint on organisms. Those species that fail to adapt must move to a different geographical landscape or become extinct.” And by "landscape" is meant "a site earth's surface, qualitatively different from other areas, bordered by natural boundaries and representing an integral and mutually conditioned natural set of objects and phenomena, which is typically expressed over a significant area and is inextricably linked in all respects with the landscape shell. Berg in his writings formulated the evolutionary concept of nomogenesis as a process proceeding according to certain internal patterns, not reducible to influences. external environment. Unlike Darwin, Berg believed that hereditary variability is regular and ordered (for example, by homological series), and natural selection does not drive evolution, but only "guards the norm." He also believed that all living things are inherent in the original expediency (as Aristotle thought when building his ladder of beings) of reactions to the influence of the external environment, while development takes place due to some force independent of the environment, directed towards the complication of biological organization. In our time, the ideas of nomogenesis were developed by the outstanding Russian biologists A. A. Lyubishchev and S. V. Meyen.
artificial mutagenesis- a new important source of creation of initial material in plant breeding.
Application ionizing radiation and chemical mutagens significantly increases the number of mutations. However, the significance of experimental mutagenesis for plant breeding was not immediately understood.
A. A. Sapegin and L. N. Delaunay were the first researchers who showed the importance of artificial mutations for plant breeding. In their experiments, conducted in 1928-1932. in Odessa and Kharkov, a whole series of economically useful mutant forms in wheat was obtained. Despite this, the use of experimental mutagenesis in plant breeding continued to be negative for a long time. Only at the end of the 50s, experimental mutagenesis was shown heightened interest. It was associated, firstly, with the major advances in nuclear physics and chemistry, which made it possible to use various sources of ionizing radiation and highly reactive chemicals to create mutations, and, secondly, with the production of practically valuable hereditary changes by these methods on a wide variety of cultures.
Particularly widespread work on experimental mutagenesis in plant breeding unfolded in last years. They are carried out very intensively in the USSR, Sweden, Japan, the USA, India, Czechoslovakia, France and some other countries. At the institute chemical physics The Academy of Sciences of the USSR, under the leadership of I. A. Rapoport, has established a center for chemical mutagenesis, which coordinates the work of many agricultural research institutions that use induced mutations as initial breeding material.
Of great value are mutations that are resistant to fungal and other diseases. The creation of immune varieties is one of the main tasks of breeding, and methods of radiation and chemical mutagenesis should play an important role in its successful solution.
With the help of ionizing radiation and chemical mutagens, it is possible to eliminate certain shortcomings in crop varieties and create forms with economically useful features: non-lodging, frost-resistant, cold-resistant, early maturing, with a high content of protein and gluten.
There are two main ways of selective application of artificial mutations: direct use of mutations obtained from the best zoned varieties, and in the process of hybridization.
The method of direct use of mutations is designed to quickly create the source material with the desired features and properties. However, the direct and rapid use of mutations, given the high requirements that are placed on modern breeding varieties, does not always give positive results. The starting material obtained as a result of mutagenesis must, as a rule, pass through hybridization. This is the second way to use artificial mutations. In the Krasnodar Research Institute of Agriculture, the mutant barley variety Temp was included in hybridization with a variety of Western European selection that was contrasting in a number of traits. This led to a huge genetic diversity of forms and the appearance of transgressive lines. From these combinations, the Kaskad spring barley variety was isolated, which surpasses the original forms in terms of yield and many other characteristics.
Mutations can change their phenotypic expression depending on which genotype they are included in. This is especially true for small physiological mutations. Therefore, crossing qualitatively changes the influence of individual mutations on the development of many traits and properties. The combination of induced mutagenesis with hybridization, the treatment of hybrid seeds F 0 , F 1 and older generations with mutagens, the crossing of mutant forms with each other and with the best zoned varieties, and backcross hybridization are also widely used. The latter is carried out according to the following scheme:
Mutant of any form with the desired X Given original improved variety with a single trait Fx X Given original improved variety 1 X Given original improved variety
Experimental mutagenesis is used and in conjunction with distant hybridization. By means of artificial mutations, in a number of cases, it is possible to overcome the non-crossing of different distant plant species, as well as to carry out transplantation by translocation of individual chromosome loci of wild species into the chromosome complex of cultivated plants. Thus, E. Sears (USA) managed to transfer from Aegilops into the wheat genome a very small piece of the chromosome that controls rust resistance. As a result, a normally fertile form was obtained, no different from wheat, but possessing rust resistance due to the translocation. In a similar way, F. Elliot transferred stem rust and smut resistance loci from wheatgrass to the wheat genome.
Of exceptional interest is the experiment of G. Stubbe (GDR) on the improvement of a wild small-fruited tomato in the process of mutagenesis. Through repeated five-stage irradiation with X-rays and selection, he brought the fruit size of this form to normal size.
A number of researchers have found that the mutability of distant hybrids is much higher than that of intraspecific and ordinary linear varieties. Numerous experiments have shown that the frequency and nature of emerging mutations in equally depend both on the type of mutagens and on the heredity of the original variety.
The choice of the initial variety for obtaining mutations is as important as the selection of parental pairs for hybridization. To create the necessary mutations, it is necessary to take into account the ability of varieties to form certain mutations, as well as the frequency of their occurrence. It was found that the closer the varieties are in their origin and genotype, the more similar they are in the frequency and nature of the emerging mutations, and, conversely, the less genetically the varieties are related, the more they differ in mutational variability. Thus, the patterns of artificial mutagenesis in different varieties obey the law homologous series in hereditary variation.
To obtain economically valuable mutations, gamma rays, X-rays and neutrons are most widely used, and among chemical mutagens, alkylating compounds: ethyleneimine, nitrosoethylurea, ethylmethanesulfonate, etc.
The concentration of chemical mutagens and doses of ionizing radiation should not be very high. To irradiate seeds, gamma rays and X-rays are used in doses from 5 to 10 kR; irradiation with fast neutrons is carried out at doses from 100 to 1000 rad. If pollen is exposed to radiation, the dose is reduced by 1.5-2 times.
Chemical mutagens are usually used in the form aqueous solutions 0.05-0.2% concentration with the duration of seed soaking from 12 to 24 hours. This ensures the best survival of plants and the preservation of mutations with economically useful traits among them. A large gap in time between seed treatment and sowing should not be allowed, otherwise germination may decrease and the damaging effect may increase. To reduce the damaging effect of mutagens, it is recommended to wash the treated seeds in running water.
Different generations of plants obtained from seeds from exposure to mutagens are designated by the letter M with the corresponding numerical indices: M-1 - the first generation, M-2 - the second, etc.
To obtain economically useful mutations in any variety, it is recommended to subject 2,000 to 4,000 seeds to a mutagenic effect. Mutation selection is most often carried out in M2. But since not all mutations are detected in M1, it is repeated in M2. Sometimes the selection starts in M1. In this case, dominant mutations are selected, as well as highly productive plants for subsequent selection in their offspring of gene mutations not associated with chromosomal rearrangements.
The first generation of mutants is grown under optimal nutrition and hydration conditions. M1 plants are threshed separately or together. With separate threshing in the second generation, individual progeny (families) of individual plants are sown, which facilitates the isolation of mutations with economically useful traits. In the second generation, mutants with well-defined valuable traits and plants are selected to obtain small mutations in the next generation. In the future, mutations are subjected to selection or used in crosses with each other or with varieties.
To date, many mutant varieties of agricultural plants have been created in the world. Some of them have significant advantages in comparison with the original varieties. Valuable mutant forms of wheat, corn, sleep and other field and vegetable crops have been obtained in recent years in research institutions in our country. Mutant varieties of winter wheat Kiyanka, spring wheat Novosibirskaya 67, barley Minsky, Temp, Debyut, soybean Universal, lupine early Kyiv, Horizon and Dnepr with a high protein content, oats Zeleny, beans Sanaris 75 and other crops have been zoned.
At the All-Union Research Institute of Oilseeds, for the first time in the world breeding by the method of chemical mutagenesis, the sunflower variety Pervenets (olive mutant) was created, the oil of which contains up to 75% oleic acid. In terms of quality, it is not inferior to the oil extracted from the fruits of the subtropical evergreen olive tree. Many mutant varieties are currently being studied under production conditions and tested at variety plots of the State Commission for Variety Testing of Agricultural Crops.
Particular attention of breeders is attracted by the use of dwarfism mutations. This problem is associated in many countries with the implementation of breeding programs to create short-stemmed varieties of intensive-type grain crops that, when irrigated and high doses of mineral fertilizers are applied, can produce grain yields of 100 c/ha and more. One of the most valuable donors of short stems in wheat turned out to be the old Japanese winter variety Norin 10, which has three pairs of spontaneously arising recessive dwarf genes dw (from the English dwarf - dwarf) with an unequal effect (dwx>dw2>dwz).
If an ordinary variety has a stem height of more than 150 cm, in semi-dwarf varieties with one dwarf gene, the stem height is 100-110 cm, and in varieties with two and three dwarf genes, respectively, 70-90 and 45-50 cm.
The work to create short-stalked wheat varieties using the Norin 10 genes at the Mexican International Center for the Improvement of Wheat and Maize (CIMMYT) has been extremely effective. Many countries have developed their own, locally adapted, short-stemmed varieties of intensive type based on Mexican dwarf wheats.
Along with the recessive genes for dwarfism of the Norin 10 variety, dominant genes are used in the breeding of intensive type varieties, the carriers of which are the Tibetan wheat Tot Roise (Tom Pus) and the Rhodesian variety Olsen Dwarfs. These genes reduce stem height in wheat even more than recessive genes. Using them, it is possible to create ultra-low-growing three-gene dwarf varieties with a stem height of 30-35 cm. It is assumed that the production of such varieties will increase the yield potential of wheat in conditions of very intensive crop farming to 150 c/ha and above. Dwarf mutants from winter wheat varieties Bezostaya 1 and Mironovskaya 808 were obtained by chemical mutagenesis at the Krasnodar Research Institute of Agriculture. good qualities grains and higher winter hardiness are widely used in hybridization.
On the basis of the mutant Krasnodarsky dwarf, a non-lodging winter wheat variety of the intensive type Semi-dwarf 49 was bred for 6 years. Breeding institutions of our country successfully use the natural EM-I mutant carrying the dominant gene of short stems to obtain highly productive varieties of winter rye.
With the help of dwarf rice mutants, it was possible to create varieties resistant to lodging, responsive to high doses of mineral fertilizers, and also distinguished by high plasticity due to the neutral photoperiodic reaction.
Valuable mutant varieties of barley were obtained in Austria, the FRG, the GDR, the USA, Czechoslovakia, and Sweden. In the Krasnodar Research Institute of Agriculture, by chemical mutagenesis, a lodging-resistant semi-dwarf 55M1 was obtained from the winter barley variety Zavet. At the same institute, a giant broad-leaved thick-stemmed oat mutant was obtained and, on its basis, the Zeleny variety was created, which gives a very high yield of fodder mass.
Mutagenesis is also used to obtain dwarf corn hybrids. For such hybrids, it is supposed to increase the yield and accelerate maturation by reducing the cost of nutrients and water for stem growth, which at the same time will allow them to be grown at a much higher plant density and used in repeated crops.
The significance of biochemical mutations is exceptionally great. Thus, in maize, spontaneous mutations of the opaque-2 (dull-2) and floury-2 (fariny-2) protein complex served as the basis for creating hybrids with a high content of essential amino acids. The recessive gene increases the content of lysine in various genotypes by 1.5-2 times. The semidominant fl2 gene has this ability to a lesser extent; under its control, the content of methionine increases significantly. This reduces the amount of zein and increases the content of other proteins richer in these amino acids. In our country, the first high-lysine hybrids of corn Krasnodar 82VL, Krasnodar 303VL, Hercules L. have been created. Their protein contains approximately 1.5 times more lysine than conventional hybrids. Animals fed with grain of high-lysine corn hybrids significantly increase their weight gain, and the cost of feed is much lower than with diets with ordinary corn.
End of the 4th century AD marked by powerful, continuous invasions of barbarian tribes within the boundaries of the Roman Empire. These were tribal unions Germans, Sarmatians, Slavs, living on the periphery of a decrepit empire.
By the time of the Great Migration of Peoples, the existing relative unity, the integrity of the territory of the Slavs were violated as a result of advancement in the II-IV centuries. AD in the Northern Black Sea region of part of the Germanic tribes, primarily ready. As a result, there has been a separation Eastern Slavs from the western ones. Later sources report on the Slavic tribes of the Wends, who lived in the region of the Laba (Elbe) River, together with the tribes Lugiev and later formed the core of the Poles, Polabian, Pomeranian Slavs (western branch). Part of the tribes of the Slavs who lived along the Danube and on the slopes of the Carpathians became part of Western groups of Slavs (Slovaks, Czechs), and the other - southern group that has mastered the land in the Balkans. Approximately in the same period, apparently, there is a process of formation Eastern branches of the Slavs, known to ancient authors under the name antes.
At the end of the II century. the invasion of the Germanic tribes of the Goths into the Northern Black Sea region, the limits of the Roman Empire, began. There the largest tribal union arose Visigoths, living north of the Lower Danube, and Ostrogoths, living across the Dniester.
Unlike most researchers, the Russian scientist L.N. Gumilyov believed that the beginning of the Great Migration of Nations should be attributed to the II century. AD, which is associated with the onslaught of the German tribes of the Ostrogoths, Visigoths and Gepids, as if cutting Europe from the north from Sweden to the Black Sea coast. We are inclined to consider the Gothic onslaught mainly in connection with the process of isolation of the Slavic cultural-territorial community in the II-IV centuries, leaving the problem of the beginning of the Great Migration open.
However, of considerable interest for understanding one of the most important mechanisms of ethnogenesis is the elucidation of the very cause or complex of causes of the phenomenon of the Great Migration of Peoples. In general, the scientific literature has established itself, let's call it conditionally, "Darwinian" the concept of ethnogenesis, which also explains the reason for the spatial movement of tribes. In accordance with it, the emergence of races and ethnic groups is associated with their struggle for existence, in which, as in the animal world, the strongest wins, capturing new territories and destroying or assimilating their inhabitants. In contrast to the prevailing view, Gumilyov proposed a theory of ethnogenesis based on the concept mutagenesis.
In accordance with it, each new species arises as a result of a mutation - a sudden change in the gene pool of living beings that occurs under the influence of external conditions in a certain place and at a certain time.
Having connected the beginning of ethnogenesis with the mechanism of mutation, which results in an ethnic “push”, leading then to the formation of new ethnic groups, Gumilyov introduces the concept "passionarity".
Passionarity is a sign that arises as a result of a mutation (passionary push) and forms within a population a certain number of people with an increased craving for action, or "passionaries".
Passionaries strive to change the environment and are capable of doing so. It is they who organize distant campaigns, from which few return. It is they who are fighting for the subjugation of the peoples surrounding their own ethnic group, or, conversely, they are fighting against the invaders. Such activity requires an increased capacity for stress, and any effort of a living organism is associated with the expenditure of a certain type of energy. This type of energy was discovered and described by our great compatriot V.I. Vernadsky and named by him the biochemical energy of the living matter of the biosphere.
Cm.: Gumilyov L.N. From Russia to Russia. M., 1922.
Gumilyov proves that passionarity in an ethnos does not remain unchanged and goes through a number of phases of development, which they liken to different ages of a person. The very life span of an ethnos, as a rule, is the same and ranges from the moment of impact to complete destruction of about 1500 years, with the exception of those cases when the aggression of foreigners disrupts the normal course of ethnogenesis.
A new cycle of development can only be caused by the next passionary push, in which a new passionary population arises. But it by no means reconstructs the old ethnos, but creates a new one, giving rise to the next round of ethnogenesis - a process due to which Mankind does not disappear from the face of the Earth.
From these positions, Gumilyov considers the process of the ethnogenesis of the Slavs, including the Russian people.
Despite the controversy of Gumilyov's concept, it cannot be denied that it allows us to approach the process of ethnogenesis of various ethnic groups from a unified position, to discover patterns, to determine the phases of the process, to answer the question of the historical fate of peoples in our own way.
Almost simultaneously with the onslaught ready in the II century. AD a powerful union is formed Huns(or Huns). Most researchers believe that the movement of the Huns, a nomadic people that developed in the II-IV centuries. in the Urals from the Turkic-speaking Xiongnu, who came from Central Asia, and local Ugrian and Sarmatians, gave impetus to the Great Migration of Peoples. In the IV century. the union of the Huns, formed on the eastern borders of the Gothic possessions, entered into a fierce battle with the Goths, subjugating a number of Germanic tribes that were part of it. In the first half of the 5th c. the union of the Huns reached its peak. The peak of his power is considered to be the reign Attila, after whose death in 453 the union of tribes fell apart.
- The Goths (Germanic tribes of the Baltic coast) began to explore the Black Sea region from the end of the 2nd century BC. n. e.
- Gumilyov L.N. From Russia to Russia: Essays ethnic history. M.: Ekopros, 1992. pp. 15-18.