Biology abstract on the topic "Material for natural selection. Mutations. The evolutionary role of mutations" (Grade 11). The evolutionary role of mutations. Currently, several million species of living organisms live on our planet, each of which in its own way

Thanks to the study of genetic processes in a population of living organisms, evolutionary theory has been further developed. A Russian scientist made a great contribution to population genetics 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.

Really, 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 100,000 - 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 heterozygous for many genes. It could be assumed that as a result of sexual reproduction, homozygous organisms will 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 overwhelming majority of cases, heterozygous organisms are better adapted to the conditions of existence 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 trunks of birches, should quickly be destroyed by enemies and the only form in these habitats should be dark-colored butterflies, homozygous for the dominant allele (AL). 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 of the mutation, as a rule, reduces 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, since they are not blown into the ocean by air masses.

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.

Mutational variability, which we met earlier, leads to the appearance of a large number of variants of each of the genes. However, mutations (gene, chromosomal and genomic) lead only to changes in genes and, accordingly, traits already present in organisms. The evolutionary development of living nature clearly demonstrates the emergence of a large array of new features and properties, especially when large taxonomic formations arise - new types and classes. Where do new signs and properties come from?

Doubling, or duplication, of hereditary material. One of the leading mechanisms leading to the emergence of new genes is DNA duplication. Depending on the size of the doubling sections, molecular geneticists distinguish intragene duplications, doubling of entire genes, chromosome sections, and some others.

The significance of such duplications for evolutionary transformations was first noted in the early 1930s. 20th century famous English biochemist J. Haldane. The scientist and his colleagues suggested that after doubling the gene, its copies can accumulate mutations in different ways. Subsequently, it turned out that the duplication of entire genes is not the only way for the emergence of new genes. Doubling a part of a gene leads to similar results, lengthening the original variant and, consequently, causing the appearance of another gene and its corresponding trait. An example of gene formation in this way is the so-called growth hormone gene family. So, as a result of duplications and mutations, genes for growth hormone, prolactin, placental lactogen, etc., arose from one initial gene.

An analysis of the genomes of organisms at different stages of the evolutionary ladder shows that the number of structural genes in them differs only by several times. For example, in a "fashionable" object in genetic studies - a large worm Caenorhabditis elegans about 20 thousand, and in humans - 25 thousand genes. At the same time, the number of traits determined by these genes in humans is several orders of magnitude higher. According to very rough estimates, 30 thousand genes of a representative of our species cause the development of more than 300 thousand traits. What is the reason for such a variety of phenotypic manifestations of such a small number of genes?

According to scientists, there are at least two such reasons.

First, these are changes in regulatory genes, leading to a change in the time and place of inclusion in the work (expression) of genes.

Activation of the gene at earlier stages of ontogeny causes and enhances the pleiotropic effect of the gene and, consequently, a greater number of its manifestations (see paragraph 13.2) in the form of several signs and properties.

Secondly, in more highly organized groups of living organisms, the very process of realization of hereditary information changes to a greater extent. Recall that when talking about transcription, we discussed the process of alternative splicing (see Section 7.2). As a result of a different connection of exons, it gives different nucleotide sequences and PHK synthesized on the same gene. Such mRNAs are translated into different proteins - different signs. When studying the processes of realization of hereditary information, it turned out that in a large worm C. elegans alternative splicing is characteristic of only 20% of genes, while in humans more than 80% of the genome is realized with the participation of this process.

Anchor points

• In real-life populations, the mutation process continuously proceeds, leading to the emergence of new variants of genes and, accordingly, traits.
• Mutations are a constant source of hereditary variation.
• The leading role in the emergence of new genes is played by intragenic and gene duplications.
• The appearance of a large number of signs in the body is due to the earlier expression of some genes and the acquisition of a pleiotropic effect by them.
• Alternative splicing significantly influences the number and diversity of organism traits.

Review questions

• 1. What population genetic patterns did the Russian biologist S.S. Chetverikov?
• 2. What is the frequency of mutation of one specific gene in the natural conditions of the existence of individuals?
• 3. How can one explain the emergence of many new genes in the course of evolution in more highly organized groups of organisms compared to less organized ones?
• 4. What is the reason for the multiple excess of the number of traits of an organism over the number of its genes?

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 tattoomeric 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. Such an evolutionary role of the 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.

Subject: Biology

Topic: "The evolutionary significance of mutations"

The purpose of the lesson: create conditions for the assimilation of the concept of mutation, consider the evolutionary role of mutations.

Lesson objectives:

Educational: patriotic education on the example of domestic scientists who have studied the mutation process;

Developing: the formation of skills and abilities of independent work, to lay the foundation for the study of genetics;

educational: to consider the essence of the mutation process, to identify its role in evolution.

Lesson type: Combined.

Conduct method: conversation, explanation, independent work group work.

During the classes:

Organizing time . Greetings. Preparing the audience for work. Checking for students.

Checking students' knowledge and goal setting .

Teacher: Now we will complete a test task, with the help of which we will find out what we will study in today's lesson. (students begin to take the test). Annex 1.

The teacher together with the students, with the help of a correctly completed test, communicate the topic of the lesson and the purpose of the lesson.

Presentation of new material.

Teacher: Write down the topic of the lesson.

Recall that evolution is divided into two types:

Evolution

microevolution macroevolution

What is the definition of microevolution? (speciation).

The teacher conducts a frontal survey to direct students to independently study this topic:

The unit of heredity is...?

Where is the chromosome located?

With the help of a drawing on the presentation and reasoning together with the teacher, the students themselves formulate a definition of the term gene. (A gene is a section of a DNA molecule that contains hereditary information).

Teacher: a living organism and each of its cells are always exposed to various environmental influences. The impact of the external environment can cause disturbances in the process of cell division and "mistakes" in the copying of genes and chromosomes. What do you think causes such “mistakes”? (mutations)

Mutation - changes in the hereditary apparatus of the cell, affecting whole cells or parts of them.

Teacher: Question to the class: What is the role of mutations in the evolutionary process? To answer this question, we will consider the mutation process in more detail. What are mutations?

Beneficial mutations: mutations that lead to increased resistance of the organism (resistance of cockroaches to pesticides). Harmful mutations: deafness, color blindness. Neutral mutations: mutations do not affect the viability of the organism in any way (eye color, blood type).

Mutation as a factor of evolution.

Teacher: Our domestic scientist S.S. was engaged in the study of natural mutations. Chetverikov. Most mutations are harmful, but rare beneficial mutations are the raw material for evolution.

The resulting recessive mutations go into a heterozygous state and are invisible. But each species (population), like a sponge, is saturated with these mutations. Thus, there is a latent variability. Since genetic diversity is the result of evolution, mutation is necessary for evolutionary progress.

Processes that change the genetic structure of a population.

It is known that in different populations of the same species, the frequency of mutant genes is not the same:

Natural disasters;

Migrations;

"Waves of numbers";

Insulation.

Students need to divide into groups and make a plan for speaking to the class on the topic of the selected process that changes the genetic structure of the population.

Summing up (reflection)

Today in class I...

The most useful thing for me was...

I encountered difficulty in...

Teacher: How would you rate today's class work?

Consolidation of the studied material (conclusion on the lesson):

What role do mutations play in evolution?

Homework. Fill in the table (Appendix 3) and answer the questions on page 58.

Annex 1.

Test on the topic: “A species is an evolutionary unit. Its criteria and structure"

Which of the following statements is most correct:

2) Which of the following organisms cannot evolve?

D) a female bee.

I) population of bees.

T) a flock of pigeons.

3) The criterion characterizing a certain area occupied by a species in nature is ...
K) Environmental criterion
B) Morphological criterion
T). Geographic criterion
D) Physiological criterion

4) The totality of geographically and ecologically close populations, capable of interbreeding, having common morpho-physiological features, is ...
A) View
H) Individual
B) population
W) Class

5) The degree of mobility of individuals is expressed by the distance that an animal can move - this distance is called ...
C) The radius of individual activity
G) Migration
D) isolation
i) There is no correct answer.

6) For species living in Baikal, the range is limited to this lake - this is an example of ... criterion
K) Ecological
T) Morphological
I) geographic
D) physiological

7) .The criterion of a species, which includes a set of environmental factors that make up the immediate habitat of the species, is ... a criterion
I) Ecological
U) Geographic
I) morphological
D) There is no correct answer.

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 will 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 the only form under these living conditions should be dark-colored butterflies, homozygous for the dominant allele (AD). 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.

In this lesson, you will learn about how mutations are related to the evolutionary process. Remember or learn what mutations are. What is their meaning? How are cancers related to evolution? In this lesson, you will learn about two types of hereditary variation (combinative and mutational) and consider mutations as a constant source of hereditary variation. You will learn about the likelihood of mutations, their consequences for organisms, and how mutations spread in a population. The principles of maintaining the genetic diversity of species due to heterozygous individuals will be considered.

Topic: Evolutionary doctrine

Lesson: The Evolutionary Role of Mutations

According to Charles Darwin, one of the main driving forces of evolution is hereditary variability. It is more or less obvious that Ch. Darwin studied hereditary variability, not possessing modern genetic ideas. Today it is known that hereditary variability is the result of the sexual process and the mutational process (see Scheme 1).

Bibliography

1. Kamensky A. A., Kriksunov E. A., Pasechnik V. V. General biology 10-11 class Bustard, 2005.

2. Belyaev D.K. Biology grade 10-11. General biology. A basic level of. - 11th ed., stereotype. - M.: Education, 2012. - 304 p.

3. Biology grade 11. General biology. Profile level / V. B. Zakharov, S. G. Mamontov, N. I. Sonin and others - 5th ed., stereotype. - Bustard, 2010. - 388 p.

4. Agafonova I. B., Zakharova E. T., Sivoglazov V. I. Biology 10-11 class. General biology. A basic level of. - 6th ed., add. - Bustard, 2010. - 384 p.