Evolutionary role of mutations brief summary. The role of mutation in evolution. Late classification of mutations

Due to the study of genetic processes in the population of living organisms, the evolutionary theory received a new impetus and further development. A great contribution to the population genetics of the Russian scientist S. Chetverikova. He drew attention to the saturation of natural populations with recessive mutations, as well as on fluctuations in the frequency of genes in populations, depending on the action of the external environment factors and justified the provision that these two phenomena are the key to understanding evolution processes.

Indeed, the mutational process is a permanent source of hereditary variability. The genes are mutated with a certain frequency. It is estimated that on average one goveta out of 10 thousand - 1 million Games carries a newly arising mutation in a certain locus. Since many gametes are mutated at the same time, then 10-15% games carry certain mutational alleles. Therefore, natural populations are saturated with a variety of mutations. Due to the combinative variability, mutations can be widely distributed in populations. Most organisms are heterozygically in many genes. It would be possible to assume that as a result of sexual reproduction among the offspring, homozygous organisms will constantly stand out, and the proportion of heterozygotes should steerly fall. However, this does not happen. The fact is that in the overwhelming majority of cases, heterozygous organisms are better adapted than homozygous.

In the example of a butterfly, a birch spine, seemingly light-colored butterflies, homozygous allele (AA), who dwells in the forest with dark trunks of birch, quickly must destroy the enemies and the only form in these habitat conditions should be dark-painted butterflies, homozygous dominant allelee (AA). But for a long time in walked birch forests, the south of England is constantly there are constant butterflies of birch spiders. It turned out that caterpillars, homozygous on the dominant allele, poorly assimilate the leaves of birches covered by Gar and Sochu, and the heterozygous caterpillars grow much better on this feed. Consequently, the large biochemical flexibility of heterozygous organisms leads to their better survival and the selection acts in favor of heterozygotes.

Thus, although most mutations in these specific conditions are harmful and in a homozygous state of mutation, as a rule, reduce the viability of individuals, they persist in populations due to the selection in favor of heterozygotes.

To understand evolutionary transformations, it is important to remember that mutations harmful in some conditions can increase viability in other conditions of the environment. In addition to the examples, you can specify the following. Mutation, causing underdevelopment or complete absence of wings in insects, is definitely harmful in normal conditions and befoldless individuals are quickly displaced normally. But on oceanic expanses and mountain passes, where strong winds blow, such insects have an advantage over individuals with normally developed wings.

Thus, the mutation process is the source of the reserve of the hereditary variability of populations. Maintaining a high degree of genetic diversity of populations, it creates the basis for the action of natural selection.

Genetic processes in populations

In different populations of one species, the frequency of mutational genes is not the same. There are practically no two populations with a perfect frequency of occurrence of mutational signs. These differences may be due to the fact that populations are inhabited in unequal conditions of the external environment. Directed change in the frequency of genes in populations is due to the action of natural selection. But closely located, neighboring populations may differ from each other as much as far away. This is explained by the fact that in populations, a number of processes lead to an uniredd random change in the frequency of genes, or, in other words, their genetic structure.

For example, when migrating animals or plants, a small part of the initial population appears at the new habitat. The arefound of the newly educated population is inevitably less than the parent population gene pool, and the frequency of genes in it will differ significantly from the frequency of genes of the original population. Genes, before the rarely encountered, as a result of sexual reproduction, they quickly apply among the new population. At the same time, widespread genes may be absent if they were not in the genotype of the founders of the new population.

Another example. Natural disasters - forest or steppe fires, floods, etc. - cause mass, inevitable death of living organisms, especially sedental forms: plants, mushrooms, mollusks, amphibians, etc. The individuals who avoided the deaths remain alive due to a pure chance. In the population survived the catastrophe, there is a decrease in the number. At the same time, the frequencies of alleles will be different than in the source population. Following the decline in the number, mass reproduction begins, the beginning of which gives the remaining, a few group. The genetic composition of this group determines the genetic structure of the entire population during its heyday. At the same time, some mutations can completely disappear, and the concentration of others may accidentally increase dramatically.

In biocenosis, periodic vibrations of populations are often observed associated with the relationship between the "predator - victim" type. Enhanced reproduction of predator hunting objects based on increasing feed resources leads, in turn, to enhanced reproduction of predators. The increase in the number of predators causes mass destruction of their victims. The lack of feed resources causes a reduction in the number of predators and restoring the size of victims. These fluctuations in numbers are called the difference waves. They change the frequency of genes in populations in which they consist of their evolutionary value.

The changes in the frequency of genes in populations also limit the exchange of genes between them, due to spatial isolation. Rivers serve an obstacle for land species, mountains and elevations. Isolate flat populations. Each of the isolated populations has specific features associated with living conditions. An important consequence of isolation is a nearby crossing - inbreeding. Thanks to the inbreeding, recessive alleles, spreading into a population, manifest themselves in a homozygous state, which reduces the viability of organisms. In human populations, isolates, with a high degree of inbreeding are found in mountainous areas and on the islands. The insulation of individual groups of caste, religious, racial and other reasons has retained.

Evolutionary value various shapes Insulation is that it enshrines and enhances genetic differences between populations, as well as that separated parts of the population or species are subjected to unequal selection pressure.

Thus, changes in the frequency of genes caused by those or other factors of the external environment serve as the basis for the emergence of differences between populations and in the future determine the transformation of them into new types. Therefore, changes in populations in the course of natural selection are called microevolution.

Control questions

1. Work S. Chetverikova in the field of population genetics.

2. Evolutionary role of mutations.

3. The mutation process is the source of the reserve of the hereditary variability of populations.

4. Changes in the frequency of genes in the population.

5. What is a microevolution?

Mutation is called persistent changes in the genotype, which occur due to the influence of external and internal factors. The term of the term is Gogo de Fris - Dutch Botany and Genetic. The process when mutations appear, referred to as mutagenesis. In today's article we will touch on the topic of mutating and talk about what the role of mutation in the process of evolution.

Causes of phenomena

It is characterized by two qualities - spontaneity and induction. The appearance is characterized by spontaneity and occurs at any stage of the body's development. Concerning ambient, it should be natural.

The type induced mutation is the hereditary change in the genome, which is due to the impact of various mutagens. Organisms are placed either into artificially created (experimental) or in unfavorable surrounding conditions.

Live cells perceive mutagenesis as a natural process for them. The main processes responsible for mutation include: replication and disruption of DNA restoration, transcription process and genetic recombination.

Mutagenez and his models

In explaining and understanding the nature and mechanisms of the appearance of mutations, special scientific approaches help. Polymerase changes are based on theory on the direct and only dependence of mutations with DNA polymer errors. In tattoral models of mutagenesis, proposed by two famous biologists, was first affected by the idea that the main layer of mutations is the possibility of DNA bases to be located in different tattoral forms.

Early classification of mutations

Genetic Meller created a classification of mutations based on the types of generation of genes. As a result, the following types appeared:

1. Amorphous. During mutation, the gene loses almost all its functions. An example of mutation can serve as changes in Drosophila.
2. Hydomorphic. The changed alleles continue to act on the same scenario as wild. Synthesizing the protein product is carried out in smaller quantities.
3. Antimorphic. Changing a mutant sign. Examples of mutation became some grains of corn - painted in not in purple.
4. Oilful.

Late classification of mutations

In modern scientific directories, there is a mention of a formal classification that is repelled from changes passing in various structures. Based on this separation, the following mutations are allocated:

1. Genomic.
2. Chromosomal.
3. Gene.

Changes with chromosomes are associated with genomic mutations, the total number of which does not correlate with a halide set.

Chromosomal mutations are attributed to the restructuring of individual chromosomes in large quantities. Genetic material in this case loses some part or, on the contrary, doubles it.

As for the gene mutation, it only slightly changes the DNA structure of the gene, unlike other species, but its emergence occurs much more often.

Inside the gene view, another subspecies, referred to as point mutation. In it, one nitrogen base is replaced by another.

It also happens that the harmfulness of mutations is gradually replaced by utility. The impetus for such changes is the ever-changing conditions for the existence of organisms. So what role do mutations play?

We take into an example natural selection is a well-known evolutionary process, which is largely dependent on variability. Consider the evolutionary role of the mutation on the example of melanist mutants (individuals with dark color), which were discovered by English scientists of the 14th century when studying birch spiders. In addition to butterflies painted in typically light colors, other individuals were found, whose color was much darker. The reason for such a strong difference was the genuated gene.

The fact is that the usual habitat for such butterflies are trees, on the trunks of which is richly growing with a lichen. Reigning in early years industrial Revolution Together with a strong pollution of the atmospheric layers led to the death of lichens. At once, the light trunks appeared soot, which prevented natural disguise all this led to the fact that the individuals, whose habitat was industrial areas, changed the color of their morph from light on the dark. Such an evolutionary role of mutation helped to survive many butterflies, while their not very successful bright conifers became victims of attacks of predatory birds.

Similar changes occur from the most a variety of species around the world. The emergence of such useful signs that are the basis of the evolutionary role of mutation leads to the fact that natural selection provides the beginning of new subspecies and species among living organisms. Mutation occurs constantly, because it is the natural ability of our genes.

More information about mutation you will find in textbooks on biology and special scientific literature.

Mutations - material evolution. Mutation is rare, randomly emerging resistant changes in the genotype, affecting the entire genome (combination of genes), whole chromosomes or parts of them. The final effect of mutation is a change in the properties of proteins. Mutational variability plays the role of the main supplier of hereditary changes. It is she who is the primary material of all evolutionary transformations.

Thus, although most mutations in these specific conditions are harmful and in a homozygous state of mutation, as a rule, reduce the viability of individuals, they persist in populations due to the selection in favor of heterozygotes. To understand evolutionary transformations, it is important to remember that mutations harmful in some conditions can increase viability in other conditions of the environment. In addition to the examples, you can specify the following. The mutation due to the underdevelopment or the complete absence of wings in insects is certainly harmful under normal conditions, and the outstanding individuals are quickly displaced normally. But on the oceanic islands and mountain passes, where strong winds blow, such insects have an advantage over individuals with normally developed wings.

In this way, the mutation process is the source of the reserve of the hereditary variability of populations.Maintaining a high degree of genetic diversity of populations, it creates the basis for the action of natural selection.

19. Population genetics

Population genetics, or genetics populations - Science, which studies the distribution of frequencies of alleles and their change under the influence of the four driving forces of evolution: mutagenesis, natural selection, gene drift and migration process. It also takes into account the subpopulation structures and the spatial structure of the population. Population genetics is trying to explain adaptation and specialization and is one of the main components of the synthetic theory of evolution.

20. Genetic characteristics of populations: hereditary heterogeneity

21. Genetic characteristics of populations: internal genetic unity

22. Genetic characteristics of populations: dynamic equilibrium of individual genotypes

The frequencies of individual alleles in the gene pool allow you to calculate genetic changes in this population and determine the frequency of genotypes. The mathematical relationship between frequencies of alleles and genotypes in populations was established in 1908. independently of the English mathematician J. Hardy and the German physician V. Weinberg. This dependence was named the Hardy - Weinberg law (equilibrium Hardy - Weinberg). This law is reading: "In an infinitely large population of freely crossing individuals in the absence of mutations, selective migration of organisms with various genotypes and pressure of natural selection, the initial frequencies of dominant and recessive alleles are stored constant from generation to generation."

From the Hardy - Weinberg equation, it follows that a significant proportion of recessive alleles existing in the population is at heterozygous media. In fact, heterozygous genotypes serve as an important potential source of genetic variability. This leads to the fact that in each generation from the population, only a very small share of recessive alleles can be eliminated. Only those recessive alleles that are in a homozygous state will be shown in the phenotype and thus subjected to selective effects of environmental factors and can be eliminated. Many recessive allelences are eliminated because they are unfavorable for phenotype - they determine either the death of the body even before he has time to leave offspring, or "genetic death", i.e. Inability to reproduction.

On the other hand, the gene drift takes place in any population of the final number, with the only difference that events are developing with a much lesser speed than with numbers in two individuals. The gene drift has two important consequences. First, each population loses genetic variability at speed, inversely proportional to its number. Over time, some alleles become rare, and then disappear at all. In the end, in the population there is a single allele from the existed, which is the case of the case. Secondly, if the population is divided into two or greater number of new independent populations, the gene drift leads to increasing differences between them: in some populations there are alone alleles, and in others - others. Processes that counteract the loss of variability and genetic discrepancies of populations are mutations and migration.

List of references:

Gorelov A.A. Concepts of modern natural science: studies. Manual for studies Higher. studies. Establishments. - M.: Humanit.Isd.Centre VLOS, 2003.- 512С.: IL.

Encyclopedia for children. Volume 23. Universal Illustrated Encyclopedic Dictionary / Chapters. ed. E.A. Hlebalina, d. ed. DI. Luri.- M.: Avanta +, 2003.- 688C.: IL.

Zakharov V.B. General biology: studies. For 10-11 cl. General. Institutions / VB Zakharov, S.G. Mamontov, N.I. Sonin.- 7th ed., Stereotype. - M.: Drop, 2004.- 624 C.: IL.

Johannsen V. L., about inheritance in populations and clean lines, M. - L., 1935;

Lobashev M.E., Genetics, L., 1967.

In all centuries, humanity tried to find answers to questions: how was this tremendous diversity formed? Why does each view are optimally adapted to the conditions of their habitat? What are the difference between some kinds from others? Why are some kinds flourish, and others die out and disappear from the face of the earth?

1. Elementary evolution unit population 2. Elementary evolution material Mutation - genotypic diversity in populations 3. Elemental evolutionary phenomenon. Long-term and directed change in the gene pool 4. Electrical evolutionary factors. Hereditary variability, struggle for existence, natural selection - guide factor 5. Elementary selection object is separate Space with a specific phenotype

S.S. The fourthics of the population like a sponge, absorb recessive mutations, while remaining phenotypically homogeneous. The existence of such an open reserve of hereditary variability creates the possibility for evolutionary transformations of the population under the influence of natural selection. Engaged in the study of natural mutations, changes in the hereditary properties of the body. Made a significant contribution to the development of population genetics.

The mutational process is a permanent source of hereditary variability. Genes are mutated with a certain frequency. In the process of sexual reproduction, the mutation can be widely distributed in populations. Most organisms are heterozygically in many genes, that is, in its cells, homologous chromosomes carry different forms of the same gene. Heterozygous organisms are better adapted than homozygous.

The mutation process is the source of the reserve of the hereditary variability of populations. Maintaining a high degree of genetic diversity of populations, it creates the basis for the action of natural selection. In different populations of one type of mutant genes of Nonodynakov. There are no populations with a completely unique frequency of the meeting of mutant signs. These differences may be due to the fact that populations are inhabited in unequal conditions of the external environment. Directed change in the frequency of genes in populations is due to the action of natural selection.

Waves of life fluctuations in the number of individuals in the population. The term is introduced by the Russian biologist S. S. Chetverikov in 1915. Such fluctuations in the number can be seasonal or non-zees, repeated through different intervals; Usually they are the longer than a longer cycle of the development of organisms. Subsequently, the term was replaced by the concept of population waves (one of the 4 elementary evolutionary factors mutation process, population waves, insulation and natural selection). The main value is reduced to random changes in the concentrations of various mutations contained in populations, as well as to weaken the selection pressure while increasing and enhancing it with a decrease in the number of individuals in the population. The term sometimes implies the stages of the development of plant and animal world, approximately corresponding to the change of geological cycles.

Evolutionary factors - factors causing the evolution of populations. "Waves of Life" and "Draif of Genes", as a rule, accompany the evolutionary process of each population if it comes to a long-term process (time period). However, historical development organic World Theoretically, possibly without them, that is, only on the basis of variability, heredity, struggle for the existence and natural selection.

Is it possible to consider all the reasons that cause the death of organisms, natural selection? Natural selection is not the only cause of the death of organisms. The death of an animal may be a consequence of a random event (forest fire, flood or other natural disaster that leaves no chance of survival).

Evolutionary factors guiding the evolutionary process of the non-directional evolutionary process of natural selection (against the background of the struggle for existence) -nous variability. - Draif genes. - Waves of life. - Isolation. Acts in the population, changing its gene pool possible result: the emergence of new populations, subspecies, species (speciation)

The combination of evolutionary processes occurring in populations of the species and leading to a change in the gene pools of these populations and the formation of new subspecies, species is called microevolution. Evolution at the level of systematic units above the species flowing millions of years and inaccessible to direct studies is called macroevolution. These two processes are united. Homework: Powers to cite examples of aromorphosis, idioadaptations and degenerations. Repeat definition, population, evolution, macroevolution, microevolution.