Thanks to the study of genetic processes in a population of living organisms, evolutionary theory has been further developed. A great contribution to population genetics was made by the Russian scientist S.S. Chetverikov. He drew attention to the saturation of natural populations with recessive mutations, as well as fluctuations in the frequency of genes in populations depending on the action of environmental factors, and substantiated the position that these two phenomena are the key to understanding evolutionary processes.

Indeed, the mutation process is a constantly acting source of hereditary variability. Genes mutate at a certain frequency. It is estimated that on average one gamete out of 10 thousand - 1 million gametes carries a newly emerged mutation at a particular locus. Since many genes mutate simultaneously, 10-15% of gametes carry certain mutant alleles. Therefore, natural populations are saturated with a wide variety of mutations. Due to combinative variability, mutations can be widely distributed in populations. Most organisms are heterozygous for many genes. It could be assumed that as a result of sexual reproduction, homozygous organisms would constantly be bred among the offspring, and the proportion of heterozygotes should steadily fall. However, this does not happen. The fact is that in the vast majority of cases, heterozygous organisms are better adapted than homozygous ones.

Let's go back to the example of the birch moth butterfly. It would seem that light-colored butterflies, homozygous for the recessive allele (aa), living in a forest with dark birch trunks, should be quickly destroyed by enemies, and dark-colored butterflies, homozygous for the dominant allele (AD) should become the only form under these living conditions. But for a long time in the sooty birch forests of southern England, light birch moth butterflies are constantly found. It turned out that caterpillars homozygous for the dominant allele do not digest birch leaves covered with soot and soot, while heterozygous caterpillars grow much better on this food. Therefore, the greater biochemical flexibility of heterozygous organisms leads to their better survival and selection acts in favor of heterozygotes.

Thus, although most mutations under these specific conditions are harmful, and in the homozygous state, mutations tend to reduce the viability of individuals, they persist in populations due to selection in favor of heterozygotes. To understand evolutionary transformations, it is important to remember that mutations that are harmful in one environment may increase viability in other environmental conditions. In addition to the above examples, the following can be pointed out. A mutation that causes the underdevelopment or complete absence of wings in insects is certainly harmful under normal conditions, and wingless individuals are quickly replaced by normal ones. But on oceanic islands 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 hereditary variability of populations. By maintaining a high degree of genetic diversity in populations, it provides the basis for natural selection to operate.

Review questions and assignments

What population-genetic patterns did the Russian biologist S.S. Chetverikov?

What is the frequency of mutation of one specific gene in the natural conditions of the existence of individuals?

What is the reason for the heterozygosity of natural populations?

What is the evolutionary role of mutations?

More on the topic Chapter 16. MICROEVOLUTION. 141. EVOLUTIONARY ROLE OF MUTATIONS:

1. THE PROGRAM OF EVOLUTIONARY DEVELOPMENT The Universal Mind has a program of evolutionary development, which is embedded in our mind at the subconscious level.

ATTENTION!!! THIS MATERIAL HAS BEEN REVISED, ADDED AND INCLUDED IN THE BOOK “Creation or Evolution? How old is the Earth? PLEASE GO TO THE PAGE TO READ -->

Aware of the lack of evidence and the arguments against interspecies evolution, neo-Darwinists put forward a new theory - "Natural selection plus mutation." That is, the source of evolutionary changes, in their opinion, are random mutations, as a result of which non-viable individuals are destroyed by the mechanism of natural selection, and successful ones live and progress further. And that's how evolution happens. However, this theory is completely wrong. Because mutation, like natural selection, does not contribute to interspecific evolution.

Mutation is the destruction of already existing DNA, which can be caused by radiation or other external influences. Mutations change the location of the nucleotides that make up the DNA molecule, causing negative consequences. There is not a single proven case where a mutation has played a positive role by improving any organism. It can only cause abnormal phenomena, for example, the growth of a leg from the back or an ear from the abdomen. Any mutant always loses something necessary for further full-fledged life and development. As a result of mutation, new information cannot be added to the DNA molecule. Thus, mutations are not able to introduce anything new into the genetic content of the cell, which means that even in essence they cannot give rise to “vertical” evolution. That is, a mutation will not make a new genus - a butterfly from a wasp. Even under control in the laboratory, it is impossible to create a new, better creation with the help of mutation. For sixty years, geneticists around the world have been changing the genes of flies to prove the theory of evolution. But a new species has not yet been bred, and not even a single more viable individual. The flies that were mutated either died immediately, were mutilated, or became sterile.

ROLE OF MUTATION IN EVOLUTION. NATURAL SELECTION

The radiocarbon method is wrong

Earth's magnetic field is weakening

"Pierced" layers

Soil erosion at the initial level

The moon is less than 10,000 years old

Population Growth Corresponds to the Biblical Age of the Earth

Moon close to Earth

Ice rings show not years

The coral reef has been growing for less than 5,000 years

Dinosaurs are reliable witnesses

All humans are descended from the same pair

Civilizations and writing less than 5,000 years old

The layers of the Earth do not have their own dating. Geological layers. Geological scale

Lack of scientific evidence. Kent Hovind

Thanks to the study of genetic processes in a population of living organisms, evolutionary theory received a new impetus and further development. The Russian scientist S. Chetverikov made a great contribution to population genetics. He drew attention to the saturation of natural populations with recessive mutations, as well as fluctuations in the frequency of genes in populations, depending on the action of environmental factors, and substantiated the position that these two phenomena are the key to understanding evolutionary processes.

Indeed, the mutation process is a constantly acting source of hereditary variability. Genes mutate at a certain frequency. It is estimated that on average one gamete out of 10 thousand - 1 million gametes carries a newly emerged mutation at a particular locus. Since many gametes mutate simultaneously, 10-15% of gametes carry certain mutational alleles. Therefore, natural populations are saturated with a wide variety of mutations. Due to combinative variability, mutations can be widely distributed in populations. Most organisms are heterozygous for many genes. It could be assumed that as a result of sexual reproduction, homozygous organisms would constantly stand out among the offspring, and the proportion of heterozygotes should steadily fall. However, this does not happen. The fact is that in the vast majority of cases, heterozygous organisms are better adapted than homozygous ones.

In the example with the butterfly, birch moth, it would seem that light-colored butterflies, homozygous for the recessive allele (aa), living in a forest with dark birch trunks, should be quickly destroyed by enemies and dark-colored butterflies homozygous for the dominant allele should become the only form in these habitat conditions. (AA). But for a long time in the sooty birch forests of the South of England, light birch moth butterflies are constantly found. It turned out that caterpillars homozygous for the dominant allele do not digest birch leaves covered with soot and soot, while heterozygous caterpillars grow much better on this food. Therefore, the greater biochemical flexibility of heterozygous organisms leads to their better survival and selection acts in favor of heterozygotes.

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

To understand evolutionary transformations, it is important to remember that mutations that are harmful in one environment may increase viability in other environmental conditions. In addition to the above examples, the following can be pointed out. A mutation that causes the underdevelopment or complete absence of wings in insects is certainly harmful under normal conditions, and wingless individuals are quickly replaced by normal ones. But on the 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 hereditary variability of populations. By maintaining a high degree of genetic diversity in populations, it provides the basis for natural selection to operate.

Genetic processes in populations

In different populations of the same species, the frequency of mutational genes is not the same. There are practically no two populations with a perfect frequency of occurrence of mutational traits. These differences may be due to the fact that populations live in unequal environmental conditions. A directed change in the frequency of genes in populations is due to the action of natural selection. But even closely located, neighboring populations can differ from each other just as significantly as distantly located ones. This is explained by the fact that in populations a number of processes lead to an undirected random change in the frequency of genes, or, in other words, their genetic structure.

For example, during the migration of animals or plants, an insignificant part of the original population appears in a new habitat. The gene pool of the newly formed population is inevitably less than the gene pool of the parent population, and the frequency of genes in it will differ significantly from the frequency of the genes of the original population. Genes, hitherto rare, are rapidly spreading through a new population through sexual reproduction. 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 massive, inevitable death of living organisms, especially inactive forms: plants, fungi, mollusks, amphibians, etc. Individuals that escaped death remain alive due to pure chance. In the population that survived the catastrophe, there is a decrease in numbers. In this case, the allele frequencies will be different than in the original population. Following the decline in numbers, mass reproduction begins, the beginning of which is given by the remaining, not numerous group. The genetic composition of this group determines the genetic structure of the entire population during its heyday. In this case, some mutations may completely disappear, while the concentration of others may accidentally rise sharply.

In the biocenosis, periodic fluctuations in the number of populations associated with relationships such as "predator - prey" are often observed. Intensified reproduction of predators' prey objects on the basis of an increase in food resources leads, in turn, to increased reproduction of predators. The increase in the number of predators causes the mass destruction of their victims. The lack of food resources leads to a decrease in the number of predators and the restoration of the size of prey populations. These population fluctuations are called population waves. They change the frequency of genes in populations, which is their evolutionary significance.

The restriction of gene exchange between them also leads to changes in the frequency of genes in populations, due to spatial isolation. Rivers serve as a barrier to terrestrial species, mountains and elevations isolate lowland populations. Each of the isolated populations has specific features associated with living conditions. An important consequence of isolation is closely related crossing - inbreeding. Due to inbreeding, recessive alleles, spreading in a population, appear 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 islands. The isolation of certain groups of the population for caste, religious, racial and other reasons has also retained its significance.

The evolutionary significance of various forms of isolation is that it perpetuates and reinforces genetic differences between populations, and that the divided parts of a population or species are subjected to unequal selection pressures.

Thus, changes in the frequency of genes caused by various environmental factors serve as the basis for the emergence of differences between populations and subsequently determine their transformation into new species. Therefore, changes in populations in the course of natural selection are called microevolution.

test questions

1. The work of S. Chetverikov in the field of population genetics.

2. The evolutionary role of mutations.

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

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

5. What is microevolution?

A mutation is a persistent change in the genotype that occurs due to the influence of external and internal factors. The ancestor of the term is Hugo de Vries, a Dutch botanist and geneticist. The process by which mutations occur is called mutagenesis. In today's article, we will touch on the topic of mutation and talk about the role of mutation in the evolutionary process.

Causes of the phenomenon

It is characterized by two qualities - spontaneity and induction. The appearance is characterized by spontaneity and occurs at any stage of development of the organism. As for the environment, it should be natural.

The induced type of mutation is a hereditary change in the genome that occurs due to exposure to various mutagens. Organisms are placed either in artificially created (experimental) or in unfavorable environmental conditions.

Living cells perceive mutagenesis as a natural process for them. The main processes responsible for mutation include: replication and impaired DNA repair, the transcriptional process, and genetic recombination.

Mutagenesis and its models

Special scientific approaches help in explaining and understanding the nature and mechanisms of the appearance of mutations. Polymerase changes are based on the theory of a direct and unique dependence of mutations on DNA polymer errors. In the tattoomer models of mutagenesis proposed by two well-known biologists, the idea was first raised that the main layer of mutations lies in the possibility of DNA bases to be located in different tattooer forms.

Early classification of mutations

The geneticist Meller created a classification of mutations based on the types of changes in the functioning of genes. As a result, the following types appeared:

1. Amorphous. During mutation, the gene loses almost all of its functions. An example of a mutation is the change in Drosophila.
2. Hypomorphic. The changed alleles continue to act according to the same scenario as the wild ones. Synthesis of the protein product is carried out in a smaller amount.
3. Antimorphic. Change in the mutant trait. Examples of the mutation are some grains of corn - they turn purple instead of purple.
4. Neomorphic.

Late classification of mutations

In modern scientific reference books there is a mention of a formal classification, which is based on changes taking place in various structures. Based on this division, the following mutations are distinguished:

1. Genomic.
2. Chromosomal.
3. Genetic.

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

Chromosomal mutations are attributed to the rearrangement of individual chromosomes in large numbers. In this case, the genetic material loses some part or, conversely, doubles it.

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

Within the gene species, another subspecies is distinguished, called a point mutation. It replaces one nitrogenous base with another.

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

Take natural selection as an example, a well-known evolutionary process that largely depends on variability. Let us consider the evolutionary role of a mutation using the example of melanistic mutants (individuals with a dark color), which were discovered by English scientists of the 14th century while studying birch moths. In addition to the butterflies, which were painted in typically light colors, other individuals were found whose color was much darker. The reason for such a strong difference was the mutated gene.

The fact is that the usual habitat for such butterflies are trees, on the trunks of which lichen grows abundantly. The industrial revolution that prevailed in the early years, together with severe pollution of the atmospheric layers, led to the death of lichens. Soot appeared on the once light trunks, which interfered with natural camouflage. All this led to the fact that individuals whose habitat was industrial areas changed the color of their morph from light to dark. This evolutionary role of mutation has helped many butterflies survive, while their not-so-successful fair relatives have become victims of attacks by birds of prey.

Similar changes are occurring in a wide variety of species around the world. The emergence of such useful traits, which are the basis of the evolutionary role of mutation, leads to the fact that natural selection gives rise to new subspecies and species among living organisms. Mutation happens all the time because it is a natural ability of our genes.

More information about mutation can be found in biology textbooks and specialized scientific literature.

1. Complete the sentence.

The priority in the study of genetic processes in the population belongs to the outstanding Russian scientist S. S. Chetvertikov.

2. Answer what is the evolutionary role of mutations.

The mutation process is the source of the reserve of hereditary variability of populations. By maintaining a high degree of genetic diversity in populations, it provides the basis for natural selection to operate.

3. Observations of natural populations show that most organisms are heterozygous for many genes. Give an explanation for this phenomenon.

Most organisms are heterozygous for many genes, that is, in their cells, paired chromosomes carry different forms of the same gene. Most often, such organisms are better adapted to the environment than homozygous ones.

4. Explain the reason(s) for differences in the genetic structure of populations of the same species.

Genetic differences between populations exist because they often live in different habitats. A directed change in the frequency of genes is due to the action of natural selection. In addition, even if populations are located close to each other, processes occur in populations that lead to an undirected, random change in the frequency of genes, that is, the genetic structure.

5. Give the definition of the gene pool of a population (species).

Population gene pool is the totality of all genes in a population.

6. Write what is the reserve of hereditary variability and what is its biological significance.

Reserve of hereditary variability is a mutation process.

Its biological significance- mutations create the basis for the genetic diversity of populations, which can later form new species. That is, mutations can lead to speciation.

7. Expand the meaning of the statement: "Some harmful mutations have positive evolutionary significance." Give an example.

In some unusual conditions, mutations help to survive and give an advantage over other individuals. For example, in some species of insects, a mutation is observed in which wings do not develop. Under normal conditions, this is harmful, but on islands and mountain passes, where strong winds blow, the absence of wings allows insects to exist normally.

8. Choose from the options below the correct answer to the question and underline it.

Which (which) of the following factors is (are) the factor-supplier (factors-suppliers) of the genetic heterogeneity of the population?

Answer: isolation, mutation process, natural selection, population waves, migration.

9. Complete the sentence.

An evolutionary factor that reinforces and consolidates genetic differences between populations is isolation.