QUESTIONS AND TASKS FOR REVIEW

Question 1. Give examples of the influence of the environment on the manifestation of a trait.

Sometimes, under the influence of certain environmental factors, stable characteristics can also change. Thus, in rabbits homozygous for the recessive ermine color gene, having a white body and black ears, tail, end of the muzzle and ends of the paws, the color pattern can be changed under the influence of temperature. N.A. Ilyin shaved areas of white and black hair from ermine rabbits and created conditions of low or high temperature. Depending on the temperature, white or black hair grew on the shaved areas of the body. For each part of the body, a threshold of irritation was set - the temperature above which white hair developed, and below which black hair developed. Thus, on the side of a rabbit at temperatures below 2 ° C, black wool grew, on the ear at temperatures above 30 ° C - white wool, etc. Thus, it is not the pattern of the rabbit that is inherited, but the ability or inability, depending on the temperature, to form pigment in hair When environmental conditions change, sometimes a trait changes in the same way as under the influence of genes, but the resulting characteristics are not hereditary. Such changes are called phenocopies. For example, in chickens, the congenital defect of taillessness is inherited, but in some cases it is caused by the influence of the external environment during the incubation period.

Question 2. Give examples that prove the non-heritability of changes in a trait caused by environmental conditions.

Many traits change during growth and development under the influence of environmental factors. Such changes in characteristics are not inherited.

The lotus and water chestnut have underwater and above-water leaves of different shapes: the lotus in the water has long, thin, lanceolate-shaped leaves, while the water chestnut has rugged, pinnate leaves.

Under the influence of ultraviolet rays, all people (if they are not albinos) develop a tan due to the accumulation of melanin pigment granules in it.

Thus, each type of organism reacts specifically to the action of a certain environmental factor, and the reaction (change in character) turns out to be similar in all individuals of a given species.

Question 3. Why is non-hereditary variability called group or specific?

Modifications are always associated with a specific environmental factor. For example, under the influence of ultraviolet radiation, the pigment melanin is synthesized and accumulated in human skin, and as a result of physical activity, the protein myoglobin is synthesized in muscle tissue, and never vice versa. In other words, phenotypic changes are determined by a given environmental factor. In addition, similar changes as a result of the action of the same environmental factor occur in all representatives of a given species, i.e. they are group changes.

Question 4. What is the reaction norm?

At the same time, the variability of a trait under the influence of environmental conditions is not unlimited. The degree of variation of a characteristic, or, in other words, the limits of variability, is called the reaction norm. The breadth of the reaction norm is determined by the genotype and depends on the significance of the trait in the life of the organism. A narrow reaction norm is characteristic of such important characteristics as, for example, the size of the heart or brain

Question 5. List and characterize the properties of modifications.

Modification variability is characterized by the following main properties: 1) non-heritability; 2) the group nature of the changes; 3) dependence of changes on the action of a certain environmental factor; 4) the dependence of the limits of variability on the genotype, i.e., with the same direction of changes, the degree of their expression in different organisms different.

Question 6. Compare the properties of mutations and modifications. Comparative characteristics of forms of variability

QUESTIONS AND TASKS FOR DISCUSSION

Question 1. How is the influence of factors reflected? environment on the manifestation of qualitative and quantitative characteristics?

Environmental factors have a greater influence on the manifestation of qualitative than quantitative traits.

Question 2. What could it be? biological significance transformation of the phenotype under the influence of environmental factors without changes in the genotype?

This biological phenomenon includes seasonal modifications. They, in turn, can be classified as environmental modifications. The latter represent adaptive changes in phenotype in response to changes in environmental conditions. Ecological modifications are phenotypically manifested in changes in the degree of expression of a trait. They can occur in the early stages of development and persist throughout life. An example would be various shapes leaves of the arrowhead, due to the influence of the environment: arrow-shaped surface, wide floating, ribbon-shaped underwater.

Question 3. How can the breadth of reaction norms affect adaptation to specific living conditions?

PROBLEM AREAS

Question 1. What are the differences in the inheritance of somatic and generative mutations? What is their significance for an individual organism and an entire species?

The primary role belongs to generative mutations that occur in germ cells. Generative mutations causing change signs and properties of an organism can be detected if a gamete carrying a mutant gene participates in the formation of a zygote. If the mutation is dominant, then a new trait or property appears even in a heterozygous individual descended from this gamete. If the mutation is recessive, then it can appear only after several generations when it becomes homozygous. An example of a generative dominant mutation in humans is the appearance of blistering of the skin of the feet, cataracts of the eye, and brachyphalanxia (short fingers with insufficiency of the phalanges). An example of a spontaneous recessive generative mutation in humans is hemophilia in individual families.

Somatic mutations by their nature are no different from generative ones, but their evolutionary value is different and is determined by the type of reproduction of the organism. Somatic mutations play a role in organisms with asexual reproduction. Thus, in vegetatively propagated fruit and berry plants, a somatic mutation can produce plants with a new mutant trait. The inheritance of somatic mutations is currently becoming important to study the causes of cancer in humans. It is assumed that for malignant tumors the transformation of a normal cell into a cancerous one occurs according to the type of somatic mutations.

Question 2. What mechanisms may underlie the appearance of mutations in living organisms?

Mutations appear constantly during processes occurring in a living cell. The main processes leading to the occurrence of mutations are DNA replication, DNA repair disorders and genetic recombination.

Question 3. What are the principles of classification of hereditary variability?

Variability can be non-hereditary and hereditary.

Hereditary variability is divided into combinative and mutational. Combinative variability is associated with recombination of parental genes.

Mutational variability is caused by mutations - stable changes in genetic material and, accordingly, an inherited trait.

APPLIED ASPECTS

Question 1: How can induced mutations produced in vitro be used to produce needed by a person signs of microorganisms?

A striking example of the use of chemical mutagens is the creation of polyploid plant varieties. People have always tried to breed those plants that had especially large fruits or produced a large harvest. In many cases, polyploids have these properties. As it turned out, these include many cultivated plants: wheat, oats, potatoes, sugar cane, plums, cherries, etc. Chemical mutagens made it possible to obtain polyploids artificially. For example, V.V. Sakharov obtained tetraploid buckwheat, a high-yielding variety with large seeds.

Question 2. What environmental factors can activate the mutation process in living organisms living in natural conditions?

To increase the frequency of mutations, it is necessary to influence cells with various mutagenic factors, such as:

1. Ultraviolet radiation;

2. Organic and inorganic compounds of natural origin (nitrogen oxides, nitrates, radioactive compounds, alkaloids).

Question 3. How can valuable traits and properties newly emerging as a result of combinative variability be consolidated?

Valuable traits that arise as a result of combinative variability are fixed in the course of natural and artificial selection.

TASKS

Question 1. Give examples of gene, chromosomal and genomic mutations in animals and plants.

An example of a genomic mutation is polyploidy. It is widespread in plants and much less common in animals (roundworms, silkworms, and some amphibians). Polyploid organisms, as a rule, are characterized by larger sizes, enhanced synthesis organic matter, which makes them especially valuable for breeding work. Example: Down syndrome in humans is trisomy 21, with a total of 47 chromosomes in a cell. Mutations can be obtained artificially using radiation, x-rays, ultraviolet radiation, chemical agents, and heat.

Question 2. Give examples of signs characterized by a wide and narrow norm of reaction. Explain how they influence the adaptation of organisms to their environment.

Knowledge of the norm of the body's reaction, the limits of its modification variability has great importance in breeding practice when “designing” new forms of plants, animals and microorganisms useful to humans. This is especially important for agricultural practice, the goal of which is to increase the productivity of plants and animals by not only introducing new breeding forms - breeds and varieties, but also maximizing the capabilities of existing breeds and varieties. Knowledge of the patterns of modification variability is also necessary in medicine for the maintenance and development human body within the normal range of reaction.

Patients with Edwards syndrome are born with low body weight (on average 2200 g).

Edwards syndrome is characterized by a combination of specific clinical manifestations: dolichocephaly, hypoplasia of the lower jaw and microstomia, narrow and short palpebral fissures, small low-lying ears, a characteristic flexion position of the fingers, a protruding occiput and other microanomalies (Fig. X.8). With the syndrome, defects of the heart and large vessels are almost constant, defects of the gastrointestinal tract, defects of the kidneys and genital organs are frequent. The life expectancy of patients with Edwards syndrome is sharply reduced. In the first year of life, 90% of patients die, by 3 years of age - more than 95%. The cause of death is defects of the cardiovascular system, intestines or kidneys.

All surviving patients have a deep degree of oligophrenia (idiocy)

Topic 26. Quantitative disorders of sex chromosomes

A change in the number of sex chromosomes can occur as a result of a violation of divergence in both the first and second divisions of meiosis. Violation of divergence in the first division leads to the formation of abnormal gametes: in women - XX and 0 (in the latter case, the egg does not contain sex chromosomes); in men - XY and 0. When gametes merge during fertilization, quantitative disturbances of the sex chromosomes occur (Table X. 1).

The incidence of trisomy X syndrome (47, XXX) is 1:1000 - 1:2000 newborn girls.

Typically, physical and mental development in patients with this syndrome there are no deviations from the norm. This is explained by the fact that two X chromosomes are activated in them, and one continues to function like in normal women. Changes in the karyotype, as a rule, are detected by chance during examination (Fig. X.9). Mental development is also usually normal, sometimes at the lower limits of normal. Only some women experience reproductive dysfunction (various cycle disorders, secondary amenorrhea, early menopause).

With tetrasomy X, high growth, a male-type physique, epicanthus, hypertelorism, flattened nasal bridge, high palate, abnormal growth of teeth, deformed and abnormally located auricles, clinodactyly of the little fingers, transverse palmar fold are noted. These women have described various menstrual irregularities, infertility, and premature menopause.

A decrease in intelligence from borderline mental retardation to various degrees of mental retardation is described in two thirds of patients. Among women with polysomy X, the incidence of mental illnesses (schizophrenia, manic-depressive psychosis, epilepsy) is increased.

Table: Possible sets of sex chromosomes during normal and abnormal course of the first meiotic division of gametogenesis


XXX triplo X

XO letal

Klinefelter syndrome was named after the scientist who first described it in 1942. In 1959, P. Jacobe and J. Strong confirmed the chromosomal etiology of this disease (47, XXY) (Fig. X.10).

Klinefelter syndrome occurs in 1 in 500 to 700 newborn boys; in 1 - 2.5% of men suffering from oligophrenia (more often with shallow intellectual decline); in 10% of men suffering from infertility.

In the neonatal period, it is almost impossible to suspect this syndrome. Basic clinical manifestations manifest during puberty. The classic manifestations of this disease are tall stature, eunuchoid physique, and gynecomastia, but all these symptoms occur simultaneously in only half of the cases.

An increase in the number of X chromosomes (48, XXXY, 49, XXXXY) in the karyotype leads to a greater degree of intellectual disability and a wider range of symptoms in patients.

Y-chromosome disomy syndrome was first described by co-authors in 1961; the karyotype of patients with this disease is 47, XYY (phc. X.11).

The frequency of this syndrome among newborn boys is 1:840 and increases to 10% in tall men (above 200 cm).

Most patients experience accelerated growth rates in childhood. The average height of adult men is 186 cm. In most cases, patients do not differ from normal individuals in physical and mental development. There are no noticeable deviations in the sexual and endocrine spheres. In 30-40% of cases, certain symptoms are observed - rough facial features, protruding eyebrows and bridge of the nose, enlarged lower jaw, high palate, abnormal growth of teeth with defects in dental enamel, large ears, deformation of the knee and elbow joints. Intelligence is either slightly reduced or normal. Emotional-volitional disorders are characteristic: aggressiveness, explosiveness, impulsiveness. At the same time, this syndrome is characterized by imitation and increased suggestibility, and patients most easily learn negative forms of behavior.

The life expectancy of such patients does not differ from the population average.

Shereshevsky-Turner syndrome, named after two scientists, was first described in 1925 by a Russian doctor, and in 1938 also clinically, but more fully, by C. Turner. The etiology of this disease (monosomy on the X chromosome) was discovered by Charles Ford in 1959.

The frequency of this disease is 1:2000 - 1:5000 newborn girls.

Most often, a cytogenetic study reveals karyotype 45, XO (Fig. X.12), however, other forms of X chromosome abnormalities are found (deletions of the short or long arm, isochromosome, as well as various

variants of mosaicism (30-40%).

A child with Shereshevsky-Turner syndrome is born only if the paternal (imprinted) X chromosome is lost (see this chapter - X.4). If the maternal X chromosome is lost, the embryo dies in the early stages of development (Table X.1).

Minimum diagnostic signs:

1) swelling of the hands and feet,

2) skin fold on the neck,

3) short stature (in adults - no more than 150 cm),

4) congenital heart defect,

5) primary amenorrhea.

With mosaic forms, a blurred clinical picture is noted. Some patients have normally developed secondary sexual characteristics and menstruation. Childbearing is possible in some patients.

Topic 27. Structural violations autosomes

The syndromes caused by an excess number of chromosomes (trisomy, polysomy) or the absence of a sex chromosome (monosomy X), i.e., genomic mutations, were described above.

Chromosomal diseases caused by chromosomal mutations are very numerous. More than 100 syndromes have been identified clinically and cytogenetically. We give one of these syndromes as an example.

The “cry of the cat” syndrome was described in 1963 by J. Lejeune. Its frequency among newborns is 1:45,000, sex ratio Ml:F1.3. The cause of this disease is the deletion of part of the short arm of chromosome 5 (5p-). It has been shown that only a small region of the short arm of chromosome 5 is responsible for the development of the full clinical syndrome. Occasionally, mosaicism due to deletion or the formation of ring chromosome-5 is observed.

The most characteristic symptom of this disease is the specific crying of newborns, similar to a cat's cry. The occurrence of a specific cry is associated with changes in the larynx - narrowing, softness of the cartilage, swelling or unusual folding of the mucous membrane, reduction of the epiglottis. These children often exhibit microcephaly, low-lying and deformed ears, microgenia, moon-shaped face, hypertelorism, epicanthus, Mongoloid eye shape, strabismus and muscular hypotonia. Children are sharply behind in physical and mental development.

Diagnostic signs such as “cat cry”, moon-shaped face and muscle hypotonia disappear completely with age, but microcephaly, on the contrary, becomes more obvious, and mental retardation also progresses (Fig. X.13).

Congenital malformations internal organs are rare, the heart is most often affected (ventricular and atrial septal defects).

All patients have severe mental retardation.

Life expectancy in patients with 5p syndrome is significantly higher than in patients with autosomal trisomies.

Annex 1

Test your knowledge

1. Define the term “variability.”

2. Let us assume that in nature there is only variability, and there is no heredity. What would be the consequences in this case?

3. What mechanisms are the sources of combinative variability?

4. What is the fundamental difference between phenotypic and genotypic variability?

5. Why is non-hereditary variability called group or specific?

6. How is the influence of environmental factors reflected on the manifestation of qualitative and quantitative characteristics?

7. What could be the biological significance of the transformation of the phenotype under the influence of environmental factors without changing the genotype?

8. By what principles can mutations be classified?

9. What mechanisms may underlie the appearance of mutations in organisms?

10. What are the differences in the inheritance of somatic and generative mutations? What is their significance for an individual organism and an entire species?

11. What environmental factors can activate the mutation process and why?

12. What environmental factors can have the greatest mutagenic effect?

13. Why does human activity increase the mutagenic effect of the environment?

14. How are mutagens used in the selection of microorganisms, plants and animals?

15. What measures are required to protect people and nature from the effects of mutagens?

16. What mutations can be called lethal? What makes them different from other mutations?

17. Give examples of lethal mutations.

18. Are there harmful mutations in humans?

19. Why is it necessary to know the structure of human chromosomes well?

20. What set of chromosomes is found in Down syndrome?

21. List chromosomal disorders that can arise from the action of ionizing radiation?

22. What types of gene mutations do you know?

23. How do gene mutations differ from genomic ones?

24. What type of mutation is polyploidy?

Appendix 2

Test on the topic "Variability. Mutations and their properties"

Option 1


B. Genotypic variability

A. Variational series
B. Variation curve
B. Norm of reaction
D. Modification

A. Phenocopies
B. Morphoses
B. Mutations
G. Aneuploidy


B. Mutational variability
G. Polyploidy

A. Chemical
B. Physical
B. Biological
D. There is no correct answer.

A. Somatic
B. Gene
B. Generative
G. Chromosomal

A. Deletion
B. Duplication
B. Inversion
G. Translocation

A. Monosomy
B. Trisomy
B. Polysomy
G. Polyploidy

A. Modifications
B. Morphoses
B. Phenocopies
G. Mutations

10.Tanning is an example...

A. Mutations
B. Morphosis
B. Phenocopies
D. Modifications


Option 2


B. Mutational variability
D. Phenotypic variability


B. Mutational variability
D. Modification variability

A. Combinative variability
B. Gene mutation
B. Chromosomal mutation
G. Genomic mutation

4. Rotating a section of a chromosome by 1800 is called...

A. Translocation
B. Duplication
B. Deletion
G. Inversion

A. Polyploidy
B. Polysomy
B. Trisomy
G. Monosomy

A. Modifications
B. Morphoses
B. Phenocopies
G. Mutations

A. Polyploidy
B. Polysomy
B. Deletion
G. Trisomy

A. Chemical
B. Biological
B. Physical
D. There is no correct answer.

A. Somatic
B. Neutral
B. Genomic
D. There is no correct answer.

A. Modifications
B. Phenocopies
V. Morphosis
G. Polyploidy


Option 3

A. Modification
B. Phenotypic
B. Genotypic
G. Non-hereditary

A. Physical
B. Biological
B. Chemical
D. There is no correct answer.

A. Combinative variability
B. Mutational variability

A. Monosomy
B. Trisomy
B. Polysomy
G. Polyploidy

A. Phenocopies
B. Mutations
B. Modifications
G. Morphoses

A. Somatic
B. Generative
B. Useful
G. Genetic

A. Polysomy
B. Trisomy
B. Polyploidy
G. Monosomy

A. Deletion
B. Duplication
B. Inversion
G. Translocation

A. Point
B. Gene
B. Genomic
D. There is no correct answer.

A. Phenocopies
B. Modifications
V. Morphosis
D. There is no correct answer.


Answers to the test on the topic "Variability. Mutations, their properties"

Answers to Option 1

1. The basis for the diversity of living organisms is:

A. Modification variability
*B. Genotypic variability
B. Phenotypic variability
D. Non-hereditary variability

2.The boundaries of phenotypic variability are called...

A. Variational series
B. Variation curve
*IN. Norm of reaction
D. Modification

3. Non-hereditary changes in the genotype that resemble hereditary diseases are...

*A. Phenocopies
B. Morphoses
B. Mutations
G. Aneuploidy

4.Changes in gene structure underlie...

A. Combinative variability
B. Modification variability
*IN. Mutational variability
G. Polyploidy

5. Radiation is... a mutagenic factor

A. Chemical
*B. Physical
B. Biological
D. There is no correct answer.

6. Mutations that affect only part of the body are called...

*A. Somatic
B. Gene
B. Generative
G. Chromosomal

7.Loss of a section of a chromosome is called...

*A. Deletion
B. Duplication
B. Inversion
G. Translocation

8. The phenomenon of loss of one chromosome is called...(2n-1)

*A. Monosomy
B. Trisomy
B. Polysomy
G. Polyploidy

9. A constant source of hereditary variability is...

A. Modifications
B. Morphoses
B. Phenocopies
*G. Mutations

10.Tanning is an example...

A. Mutations
B. Morphosis
B. Phenocopies
*G. Modifications


Answers to Option2

1. Variation that does not affect the genes of the organism and does not change hereditary material, called...

A. Genotypic variability
B. Combinative variability
B. Mutational variability
*G. Phenotypic variability

2.Indicate directional variability:

A. Combinative variability
B. Mutational variability
B. Relative variability
*G. Modification variability

3.Changes in the number of chromosomes are the basis...

A. Combinative variability
B. Gene mutation
B. Chromosomal mutation
*G. Genomic mutation

4. Rotating a section of a chromosome by 180 degrees is called...

A. Translocation
B. Duplication
B. Deletion
*G. Inversion

5. Shereshevsky-Turner syndrome can occur as a result of...

A. Polyploidy
B. Polysomy
B. Trisomy
*G. Monosomy

6. Non-hereditary changes in the genotype that occur under the influence of environmental factors are adaptive in nature and most often reversible - this is...

*A. Modifications
B. Morphoses
B. Phenocopies
G. Mutations

7. The phenomenon of changing the number of chromosomes, a multiple of the haploid set, is called...

*A. Polyploidy
B. Polysomy
B. Deletion
G. Trisomy

8. Alcohol is... a mutagenic factor

*A. Chemical
B. Biological
B. Physical
D. There is no correct answer.

9. Mutations that lead to increased resistance of the body are called...

A. Somatic
B. Neutral
B. Genomic
*G. There is no correct answer

10. An increase in red blood cells in the blood with a lack of oxygen is an example...

*A. Modifications
B. Phenocopies
V. Morphosis
G. Polyploidy


Answers to Option3

1.Indicate non-directional variability:

A. Modification
B. Phenotypic
*IN. Genotypic
G. Non-hereditary

2. Colchicine is... a mutagenic factor

A. Physical
B. Biological
*IN. Chemical
D. There is no correct answer.

3. Crossover is a mechanism...

*A. Combinative variability
B. Mutational variability
B. Phenotypic variability
D. Modification variability

4. The phenomenon of acquiring one chromosome is called...(2n+1)

A. Monosomy
*B. Trisomy
B. Polysomy
G. Polyploidy

5. Non-hereditary changes in phenotype that occur under the influence of extreme environmental factors, are not adaptive in nature and are irreversible, are called...

A. Phenocopies
B. Mutations
B. Modifications
*G. Morphoses

6. Mutations that occur in germ cells (and therefore are inherited) are called...

A. Somatic
*B. Generative
B. Useful
G. Genetic

7. Klinefeltre's syndrome can occur as a result of...

A. Polysomy
*B. Trisomy
B. Polyploidy
G. Monosomy

8. The transfer of an entire chromosome to another chromosome is called...

A. Deletion
B. Duplication
B. Inversion
*G. Translocation

9. Mutations associated with changes in the structure of chromosomes are called...

A. Point
B. Gene
B. Genomic
*G. There is no correct answer

10.Loss of limbs is an example...

A. Phenocopies
B. Modifications
*IN. Morphosis
D. There is no correct answer.

Appendix 3

test on the topic “Variability”.

Task No. 1

Organisms adapt to specific environmental conditions without changing the genotype due to variability

a) mutational

b) combinative

c) relative

d) modification

2. Do leaves plucked from one tree have variability?

a) mutational

b) combinative

c) modification

d) all leaves are the same, there is no variability

3. The role of modification variability

a) leads to a change in genotype

b) leads to recombination of genes

c) allows you to adapt to different environmental conditions

d) doesn't matter

4. Modification variability as opposed to mutational variability:

a) usually manifests itself in most individuals

b) characteristic of individual individuals of the species

c) associated with gene changes

d) is hereditary

5. An increase in body weight in domestic animals due to changes in diet is classified as variability:

a) modification

b) cytoplasmic

c) genotypic

d) combinative

Task No. 2

Fill in the table with numbers.

Modification variability

Mutational variability

What sign relates to these mutations?

1. The phenotype is within the normal range of reaction.

2. Chromosomes do not undergo changes.

3. The form of variability is group.

4. law homologous series hereditary variability.

5. Useful changes lead to victory in the struggle for existence.

6. Promotes survival.

7. DNA molecules are not subject to variability.

8. Selecting factor – change in environmental conditions.

9. Inheritance of characteristics.

10. Increases or decreases productivity.

Task No. 3

Fill in the table with numbers.

Modification variability

Mutational variability

1. They arise gradually and have transitional forms.

2. They arise under the influence of the same factor.

3. They appear intermittently.

4. May occur repeatedly.

5. Not passed on from generation to generation.

6. Reversible.

7. The same and different genes can mutate under the influence of the same factor.

8. Passed on from generation to generation.

9. The basis of existence is phenotype.

10. The basis of existence is the genotype.

Task No. 4

Match:

I By level of occurrence

1.Generative

II By place of origin

2.Biochemical

III By type of allelic relationships

3.Lethal

IV By influence on the viability of an individual

4. Spontaneous

V By nature of manifestation

5.Amorphous

VI According to phenotypic origin

6.Genomic

VII By origin

7.Induced

8. Dominant

9.Intermediate

10. Harmful

11.Somatic

12.Antimorphic

13.Neutral

14.Physiological

15.Recessive

16.Hypomorphic

17.Useful

18.Morphological

19.Chromosomal

21.neomorphic

To I

To II relate _______________________

To III _

To IV relate _______________________

To V relate _______________________

To VI relate ______________________

To VII relate ______________________

  1. Phenotype as a result of the implementation of a genotype in a certain environment.
  2. Quantitative and qualitative specificity of the manifestation of genes in traits.
  3. Interaction of nonallelic genes.

Genome– a set of genes characteristic of the haploid set of chromosomes of a given species. During fertilization, the genomes of the parents combine to form the cell genotype of the zygote.

Genotype– the totality of all the genes of an organism (genetic constitution). From the genotype of the zygote during ontogenesis, many hundreds of different cellular phenotypes arise. Individual cellular phenotypes shape the phenotype of the entire organism. The entire process of life from the formation of the zygote to natural death is controlled by genes. The genotype is constantly exposed to the influence of the external environment, it interacts with the environment, which leads to the formation of all the characteristics and properties of the organism.

Phenotype– all the characteristics of an organism that are formed as a result of the interaction of genotype and environment. (Johansen - 1803) the properties of any organism depend on the genotype and on the environment, therefore the formation of an organism is the result of the interaction of genetic factors and environmental factors.

For a long time it was believed that the zygote contains different chromosomes for different cells, however, it is now known that the zygote contains the same genetic information, as in all cells of a given organism. In specialized cells, genes characteristic of the functions of these cells operate, and all the rest - up to 95% - are blocked. Each embryonic cell has the potential to become any cell in the body, i.e. specialize in any direction - pluripotent cells. Each cell of the body is capable of differentiation in only one way. The direction of specialization is determined by the external environment (the chemical environment of the chromosomes - the cytoplasm). At the earliest stages of embryogenesis, the genotype already interacts with the environment. It is convenient to view the interaction using the example of globin genes. Before and after birth, these genes work differently. In early embryogenesis, the gene responsible for the alpha chain of hemoglobin is turned on (it is active throughout life), and the gene responsible for the synthesis of the beta chain is inactive. But there is a gene responsible for the synthesis of the gamma chain. After birth, the beta chain gene begins to work, and the gamma chain is blocked. These changes are associated with breathing patterns. Fetal hemoglobin easily carries air to the embryo.

The phenotypic manifestation of the genotype, depending on the environment, varies within the normal range of the reaction. From parents, offspring receive specific types chemical reactions to different environmental conditions. The totality of all chemical reactions determines metabolism - metabolism. The metabolic rate varies widely. Each person has his own metabolic characteristics, which are passed on from generation to generation and are subject to Mendelian laws. Differences in metabolism are realized under specific environmental conditions at the level of protein synthesis.

Differential response of primrose plants under different environmental conditions. At normal temperatures of 20-25 degrees and normal pressure - red flowers, at elevated temperatures or pressure - white flowers. The seeds have the same properties.

The Drosophila fly has a gene that causes the wings to close on the back. If flies with mutant genes are hatched at a temperature of 22-25 degrees, the wings are bent. At lower temperatures, the wings are normal and only some have bent wings. The gene determines the synthesis of a thermosensitive protein. Therefore, drying out after emerging from the pupa, deformation of the wings occurs at elevated temperatures.

No traits are inherited. Traits develop based on the interaction of genotype and environment. Only the genotype is inherited, i.e. a complex of genes that determines the norm of the biological reaction of the body, changing the manifestation and severity of symptoms in different environmental conditions. Thus, the body reacts to the properties of the external environment. Sometimes the same gene, depending on the genotype and environmental conditions, manifests a trait differently or changes the completeness of expression.

The degree of manifestation of the phenotype – expressiveness b. Figuratively, it can be compared with the severity of the disease in clinical practice. Expressiveness obeys Gaussian distribution laws (some in small or medium amounts). Variation in expressiveness is based on both genetic and environmental factors. Expressivity is a very important indicator of the phenotypic manifestation of a gene. Its degree is quantified using a statistical indicator.

The genetic trait may not even appear in some cases. If a gene is in the genotype, but it does not appear at all, it is penetrated. (Russian scientist Timofeev-Risovsky 1927). Penetrance– the number of individuals (%) exhibiting a given gene in the phenotype, in relation to the number of individuals in which this trait could manifest itself. Penetrance is characteristic of the expression of many genes. The important principle is “all or nothing” - either it manifests itself or it doesn’t.

Hereditary pancreatitis – 80%

Hip dislocation – 25%

Eye malformations

Retinoblastoma – 80%

Otosclerosis – 40%

Kolotokoma – 10%

Huntington's chorea manifests itself as involuntary jerking of the head. Limbs, gradually progresses and leads to death. It may appear in the early postembryonic period, in adulthood, or not appear at all. Both expressivity and penetrance are maintained by natural selection, i.e. genes that control pathological signs may have different expressivity and penetrance: not all carriers of the gene become ill, and in those who are sick, the degree of manifestation will be different. The manifestation or incomplete manifestation of a trait, as well as its absence, depends on the environment and on the modifying effect of other genes.

1919 Bridges coined the term modifier gene. Theoretically, any gene can interact with other genes, and therefore exhibit a modifying effect, but some genes are more modifiers. They often do not have their own trait, but are able to enhance or weaken the manifestation of a trait controlled by another gene. In the formation of a trait, in addition to the main genes, modifying genes also exert their effect.

Brachydactyly - can be severe or minor. In addition to the main gene, there is also a modifier that enhances the effect.

Coloring of mammals – white, black + modifiers.

The gene can act pleiotropic(plural), i.e. indirectly influence the course of various reactions and the development of many signs. Genes can influence other traits at different stages of ontogenesis. If the gene is turned on in late ontogenesis, then there is an insignificant effect. If in the early stages, the changes are more significant.

Phenylketanuria. Patients have a mutation that turns off the enzyme phenylalanine hydrolase. Therefore, phenylalanine is not converted to tyrosine. As a result, the amount of phenylalanine in the blood increases. If this pathology is detected early (before 1 month) and the child is switched to a different diet, development proceeds normally; if later, the brain size is reduced, mental retardation, does not develop normally, there is no pigmentation, mental abilities are minimal.

Pleiotropy reflects the integration of genes and traits.

A person has an abnormal gene that leads to Fanconi syndrome (a malformation or absence of thumb, defect or absence of the radius, underdevelopment of the kidney, brown pigment spots, lack of blood cells).

There is a gene associated with the X chromosome. Immunity to infections and lack of blood cells.

A dominant gene linked to the X chromosome is pilonephritis, labyrinthine hearing loss.

Marfani syndrome – spider fingers, dislocation of the eye lens, heart defects.

Polymerism. If genes are located, each in its own separate locus, but their interaction manifests itself in the same direction - these are polygenes. One gene exhibits the trait slightly. Polygenes complement each other and have a powerful effect - a polygenic system arises - i.e. the system is the result of the action of identically directed genes. Genes are significantly influenced by the main genes, of which more than 50 polygenic systems are known.

Mental retardation is observed in diabetes mellitus.

Height and level of intelligence are determined by polygenic systems

Complementarity– a phenomenon in which there are 2 non-allelic genes. Being in the genotype, they simultaneously lead to the formation of a new trait. If one of the pair is present, it manifests itself.

An example is human blood groups.

Complementarity can be dominant or recessive.

In order for a person to have normal hearing, many genes, both dominant and recessive, must work in concert. If he is homozygous recessive for at least one gene, his hearing will be weakened.

Epistasis– such an interaction of genes when the gene of one allelic pair is masked by the action of another allelic pair. This is due to the fact that enzymes catalyze different cellular processes when several genes act on one metabolic pathway. Their action must be coordinated in time.

Mechanism: if B turns off, it will mask the action of C

B – epistatic gene

C – hypostatic gene

Mccusick:

“The relationship between genotype and phenotype is the same as between a person’s character and his reputation: genotype (and character) is the inner essence of an individual, phenotype (and reputation) is how he looks or appears to others.”

LECTURE No. 9

Variability.

1. Modification variability.

2. Combinative variability.

3. The marriage system.

4. Mutational variability.

One of the signs of life is variability. Any living organism is different from other members of its species. Variability- the property of living organisms to exist in different forms. Group And individual variability - classification according to evolutionary significance. Variability realized by a group of organisms is called group, while in one organism or a group of its cells it is individual.

According to the nature of changes in signs and mechanism:

Phenotypic

Random

Modification

Genotypic

Somatic

Generative (mutational, combinative)

a) genetic

b) chromosomal

c) genomic

Modification variability reflects a change in phenotype under the influence of environmental factors (strengthening and development of muscle and bone mass in athletes, increased erythropoiesis in high mountains and the far north). Special case phenotypic variability – phenocopies. Phenocopies– phenotypic modifications caused by environmental conditions that imitate genetic traits. Under the influence of external conditions, signs of a completely different genotype are copied on a genetically normal organism. The manifestation of color blindness can occur under the influence of nutrition, poor mental constitution, and increased irritability. A person develops the disease vitiligo (1% of people) - a disorder of skin pigmentation. 30% of sufferers have a genetic defect, the rest have occupational vitiligo (exposure to special chemicals and toxic substances on the body). In Germany 15 years ago, children were born with fecomelia - shortened, flipper-like arms. It revealed. That the birth of such children occurred if the mother took Telidomide (a sedative indicated for pregnant women). As a result, the normal non-mutant genotype received a mutation.

Phenocopies appear in most cases under the influence of the external environment in the early stages of embryogenesis, which leads to congenital diseases and developmental defects. The presence of phenocopies makes it difficult to diagnose diseases.

Somatic variability not inherited.

Combinative variability- the result of independent chromosome divergence during the process of meiosis, fertilization, crossing over with gene recombination. With combinative variability, recombination of genes occurs, a new individual set of chromosomes arises, and therefore a new genotype and phenotype. For combinative variability in the human system, the marriage system is of great importance. The simplest is random selection of pairs (panmixia). Strictly panmix populations do not exist, because There are restrictions: social, religious, individual, economic and others. Therefore, in human populations there are deviations from panmixia in two directions:

1) People who are related to each other marry more often than with random selection - inbreeding - inbreeding (consanguineous marriages).

2) People marry more often through random selection of couples than through consanguineous marriages - autobreeding.

Inbred marriages are of great medical importance. Because the likelihood that both spouses have the same recessive genes is much higher if the spouses are related to each other, especially closely. The relationship is natural. From a medical point of view, selective marriages based on phenotypic characteristics are considered to be close in genetic effect. If the choice of a marriage partner influences the genotype of the offspring - assortative marriages. People who are phenotypically similar are more likely to marry than with a random selection of pairs - positive assortative marriages, if less often - negative ones. Examples include marriages between deaf and mute people, tall people, and people of the same skin color. Negative assortative marriages between red-haired people.

Consanguineous marriages were common in the early stages of human development.

There are 3 inbreeding groups:

1. between first-degree relatives

2. consanguineous marriages of isolated populations

3. encouraged consanguineous marriages for social, religious and other reasons.

Incestuous (forbidden) marriages between relatives of the first kinship: mother-son, father-daughter, brother-sister. Took place in Egypt, the Ptolemaic dynasty. In a number of eastern countries, the family of Ivan the Terrible (starting with Ivan Kalita - several similar marriages).

Legal restrictions: marriages between cousins, nephews and aunts, nieces and uncles are allowed. Although there are restrictions in some countries. USA and UK - uncle-niece, half-uncle-niece - are prohibited. In the USA, cousins ​​are prohibited, in the UK they are allowed.

Consanguineous marriages in isolated areas (isolates), incl. and religious isolates are inevitable, because otherwise the population dies out.

In large non-isolated populations, consanguineous marriages account for 1% in the city and 3% in villages, up to second cousins. Consanguineous marriages are encouraged among Jews, in eastern countries. There's up to 12%.

In Samarkand region

Uncle-niece 46

Nephew-Aunt 14

Cousins ​​42

Incest 2

Inbreeding coefficient - average identical by origin.

USA, Catholics – 0.00009

Israel and Jordan – 0.432

India – 0.32

Japan – 0.0046

In India, half of marriages are between relatives; infant mortality for any income is 50%.

Genetic effect of consanguineous marriages: rare autosomal recessive diseases become common.

The frequency of occurrence of recessive genes, compared to marriages between people who are not related, increases sharply in marriages between relatives.

Mutational variability- the only type of variability that can result in the appearance of new genes that may not have been encountered before. The genotype changes and, as a result, the phenotype changes. In accordance with the three levels of organization of genetic material, 3 types of mutations are distinguished: gene, chromosomal and genomic.

Mutation - a sudden hereditary change in any phenotypic trait caused by a sharp structural or functional change.

Gene mutations are associated with changes in the internal structure of genes, which transforms one allele into another. Several types of gene mutations can be distinguished: molecular level:

Substitution of nucleotide pairs

Deletion

Nucleotide insertion

Rearrangement (inversion) of a gene region.

Substitution of nucleotide pairs . Replacing a purine base with another purine base, or one pyrimidine base with another pyrimidine base – transition. Replacing a purine base with a pyrimidine base and vice versa - transversion. When nucleotides are replaced in structural genes, the meaning of the gene changes - missense mutations. In this case, one amino acid in the polypeptide is replaced by another. The phenotypic manifestation of the mutation depends on the position of the amino acid in the polypeptide. When the CTC sequence is replaced by CAC, sickle cell anemia occurs. A new polypeptide is formed and hemoglobin has completely different properties. Some missense mutations result in an enzyme that is highly active under some conditions and moderately active under other conditions. Because genetic code is degenerate, then when replacing triplets encoding the same amino acid, mutations do not appear. Another type of mutation is nonsense - mutations. With these mutations, when one nucleotide is replaced by another, meaningless triplets are formed. The synthesis of the polypeptide stops and the protein has completely different properties.

Test tasks

* Test items with multiple correct answers

1. In a monohybrid cross, the first generation hybrids are phenotypically and

genotypically uniform - Mendel's law: 1) 1; 2) 2; 3) 3; 4) 4.

2. *Monoheterozygote is: 1) Aa; 2) AA; 3) AaBB; 4) Aavv; 5) aa; 6) AABB; 7) AaBb.

3. *Analyzing crossing is: 1) ♀Aa× ♂Aa; 2)♀ Aa× ♂ aa; 3) ♀аа× ♂аа; 4)♀ аа× ♂ Аа.

4. *Possible genotypes of offspring from crossing a polled (dominant trait) heterozygous cow with a horned bull: 1) all bb; 2) BB; 3) Bb; 4) all BB; 5) bb.

5. In test crossing, hybrid F is crossed 1 with homozygote: 1) dominant; 2) recessive.

6. Crossing two heterozygotes (complete dominance) in the offspring there will be a splitting of the phenotype: 1) 9:3:3:1; 2) 1:1; 3) 3:1; 4) 1:2:1.

7. The set of genes in a cell: 1) genotype; 2) genome; 3) karyotype; 4) phenotype; 5) gene pool.

8. *A trait is called dominant if: 1) it is inherited in F hybrids 1 2) manifests itself in heterozygotes; 3) does not appear in heterozygotes; 4) occurs in most individuals in the population.

9. Phenotype splitting in F 2 with incomplete dominance in a monohybrid cross: 1) 9:3:3:1; 2) 1:1; 3) 3:1; 4) 1:2:1.

10. *The gray color of the rabbit's fur is dominant over the white. Gray rabbit genotype: 1) aa; 2) AA; 3) Aa; 4) AB.

11. As a result of crossing strawberry plants ( incomplete dominance– red, white and pink color of fruits) with genotypes Aa and aa phenotypic ratio of offspring: 1) 1 red: 1 white; 2) 1 red: 1 pink; 3) 1 white:

1 pink; 4) 1 red: 2 pink: 1 white.

12. As a result of crossing chickens (incomplete dominance: black–blue–white plumage color) with genotypes Aa and Aa phenotypic ratio of offspring: 1) 1 black: 1 white; 2) 3 black: 1 blue; 3) 3 black: 1 white; 4) 1 black: 2 blue: 1 white; 5) 1 blue: 1 white; 6) 3 blue: 1 white.

13. *Dominant homozygote is: 1) AaBB; 2) aabb; 3) AABB; 4) AABb; 5) AABBCC.

14. Gamete ABCD is formed by the genotype: 1) AabbCcDD; 2) AABbCcdd; 3) AaBbccDd; 4) aaBbCCDd.

15. *Drosophila has a black (recessive trait) body and normal wings (dominant trait) - genotype: 1) AABB; 2) AaBb; 3) aabb; 4) AaBB; 5) aaBb; 6) AABb; 7) Aabb; 8) aaBB.

16. *The rabbit has shaggy (dominant trait) white (recessive trait) fur - genotype: 1) AAbb; 2) AaBb; 3) aabb; 4) AaBB; 5) aaBb; 6) AABb; 7) Aabb; 8) aaBB.

17. *Peas have tall plants (dominant trait) and red flowers

(dominant trait) – genotype: 1) aabb; 2) AABb; 3) Aabb; 4) AABB; 5) AaBb; 6) AaBB; 7) Aabb.

3.7. Basic patterns of variability

IN surveys for review and discussion

1. What processes lead to combinative variability?

2. What is the basis for the uniqueness of each living organism at the genotype and phenotype level?

3. What environmental factors can activate the mutation process and why?

4. How does the inheritance of somatic mutations differ from generative ones and what is their significance for the organism and species?

5. What are the movement mechanisms? mobile elements Can you name it by genome?

6. Why does human activity increase the mutagenic effect of the environment?

7. What biological significance can transformation of the phenotype have without changing the genotype?

8. Why are modifications generally beneficial to the body?

Test tasks

1. Phenotype is a collection

internal

characteristics of the body. Consider-

differences in phenotype. Express

assumptions about the reasons

phenotypes

2. Observations on meta-

Drosophila morphosis showed: a)

if you feed Drosophila larvae

add a little silver nitrate,

Rice. 3.98. Variability of horns

then yellow individuals are hatched,

due to their homozygosity for the dominant gray body color gene (AA); b) in individuals homozygous for the recessive gene for the rudimentary wings (bb), at a temperature of 15°C the wings remain rudimentary, and at a temperature of 31°C normal wings grow. What can you say based on these facts about the relationship between genotype, environment and phenotype? Does the transformation of a recessive gene into a dominant one occur in these cases or vice versa?

3. Any sign can vary within certain limits. What is a reaction norm? Give examples of characteristics of organisms that have a broad and narrow reaction norm. What determines the breadth of a reaction norm?

4. Calculate average value(M) and construct a variation curve based on the following data (Tables 3.8; 3.9).

Table 3.8.

Variability in the number of reed flowers in a chrysanthemum inflorescence

Number of flowers

inflorescences

Number of inflorescences

Table 3.9.

Variability in the number of bone rays in the caudal fin of the flounder

Number of rays

fin

Number of individuals

5. In the Chernobyl area, after the disaster at the nuclear power plant, mutant animals began to appear, and the incidence of thyroid cancer in people increased. What do these facts indicate? Why do mutant fish with huge heads, no scales, one eye, and no color appear in the rivers of large cities polluted by industrial waste? Give an explanation for this phenomenon.

Consider

3.99. Body weight of a large

cattle, like others

animals – typical coli-

honest sign.

Development

quantitative

signs

Rice. 3.99. Two yearling bulls

Install

ages descended from one

what type of variability resulted

father, but raised in different

to a change in mass

the bodies of these

conditions

one of which is semi-

ate food in excess, while the other ate very little.

7. Consider the different leaf shapes of arrowhead, (Fig. 3.100), which is a classic example of modification variability. Determine what causes the differences in leaf shape in arrowhead plants grown in different conditions.

8. Consider the changes in hair color of an ermine rabbit under the influence of different temperatures (Fig. 3.101). Determine the type of variability.

Rice. 3.100. Leaf Shape

arrowhead during development in different environments

Rice. 3.101. Changing the color of the Himalayan's coat

rabbit under the influence of different temperatures

Laboratory workshop

1. A series of multiple alleles - a pattern of gray spots on clover leaves. Get acquainted with the herbarium of clover leaves and trace the pattern of inheritance of the trait of gray spots. The gene that determines this trait is represented by the eight most common alleles. Compare the drawing on the herbarium sheet with the drawings shown in the diagram (Fig. 3.102) and determine the genotype.

There is incomplete dominance. It is impossible to determine the genotype of only those forms where the spot patterns determined by the two alleles merge or there is complete dominance. For example, VBVH and VHVH have the same phenotype, VBVP and VBVB also do not differ phenotypically, since VB is dominant over VH and VP; VFVP and VFVL are indistinguishable from VFVF due to the fusion of patterns. Heterozygotes cv also do not differ from dominant homozygotes.

Sketch the specimens offered to you and determine their genotypes or phenotypic radicals, write down the symbols. Make a series of all the alleles encountered.

Rice. 3.102. Diagram of patterns of gray spots on clover leaves indicating

genotype

(vv – no spot; VV – solid ^-shaped spot; VHVH – solid high ^-shaped spot; VBVB – ^-shaped spot with a break; VBhVBh – high ^-shaped spot with a break; VPVP – ^-shaped spot in the center ; VFVF – solid triangular spot on the base; VLVL – solid small triangular spot on the base.

2. Determination of a person’s individual ability to perceive the bitter taste of phenylthiourea (PTM). Using tweezers, place first a control and then an experimental strip of filter paper on the back of the tongue, determine your individual ability (inability) to perceive the bitter taste of PTM, i.e. sign of FTM+ or FTM-. Make a conclusion about your possible genotype, keeping in mind that the FTM+ trait is controlled by the dominant gene (T).

Conditionally considering the student group as a separate population, determine the population frequency of the trait FTM+ (or FTM-) as the proportion of the number of individuals who are carriers of the trait in the total number of those surveyed.

Calculate the genetic structure of the population (frequency of allelic genes and possible genotypes) using the HardyWeinberg formula: p² + 2pq + q² = 1, where p² is the frequency of homozygotes for the dominant allele (TT genotype), 2pq is the frequency of heterozygotes (Tt),q²

– frequency of homozygotes for the recessive allele (tt) in the study population. When calculating the frequencies of the dominant (T) and recessive allele (t) present in the population, the formula p + q = 1 should be used.

Test tasks

* Test tasks with multiple correct answers

1. Chemical compounds that induce mutations: 1) metagenes; 2) methylenes; 3) mutagens.

2. *The main mechanisms of the mutation process are violations of the following matrix processes: 1) translation; 2) replication; 3) transcriptions; 4) reparations.

3. A non-inherited change is called: 1) reversion; 2) isolation; 3) modification.

4. *High variability of quantitative traits is due to: 1) polygenic nature of inheritance; 2) the influence of environmental factors; 3) genotypic heterogeneity; 4) homozygotization during the selection process.

5. *The genetic activity of the following genetic factors has been identified: 1) electricity; 2) x-ray radiation; 3) gamma radiation; 4) ultraviolet radiation; 5) extreme temperatures.

6. Inherited from parents to descendants: 1) trait; 2) modification; 3) reaction norm; 4) phenotype; 5) modification variability.

7. The form of variability, as a result of which a left-handed blue-eyed child was born to right-handed, cross-eyed parents: 1) mutational; 2) combinative; 3) modification; 4) random phenotypic.

8. The form of variability, as a result of which, with the onset of winter, the animal experienced a change in color and thickness of hair: 1) mutation; 2) combinative; 3) modification; 4) random phenotypic.

9. The form of variability, as a result of which a child with six fingers was born in a family of five-fingered parents (a recessive trait): 1) mutational; 2) combinative; 3) modification; 4) random phenotypic.

10. *The reason for the increase in the frequency (occurrence) of several pathological alleles in the human population: 1) an increase in the level of radiation contamination;

2) immigration from areas with unfavorable environmental conditions; 3) increasing the birth rate; 4) increase in life expectancy; 5) improving the level of medical care.

11. A characteristic feature of modifications, in contrast to mutations: 1) material for evolution; 2) their formation is accompanied by a change in the genotype; 3) usually useful; 4) are inherited.

12. In adult ermine rabbits living in natural conditions, most of the body has white hair, and the tail, ears and muzzle are black, which is due to the difference in body areas in skin temperature - this is a manifestation of a form of variability: 1) mutational; 2) combinative; 3) modification; 4) random phenotypic.

13. A form of variability, as a result of which, with the onset of puberty, the timbre of a young man’s voice changed and a mustache and beard appeared: 1) mutational; 2) combinative; 3) modification; 4) random phenotypic.

14. Type of typical variation curve: 1) straight line; 2) dome-shaped curve; 3) exhibitor; 4) circle.

15. *A persistent increase in the frequency of one of the dominant genes in an animal population is associated with the following the most probable reasons: 1) changes in living conditions; 2) an increase in the birth rate; 3) the migration of some animals;

4) extermination of animals by humans; 5) lack natural selection.

Part 4.

POPULATION-SPECIES LEVEL OF ORGANIZATION

Organic evolution is an objective process.

A population is an elementary evolutionary unit. The main characteristics of the population as an ecological-genetic system (population area, number of individuals in the population, age composition, sex composition, basic morpho-physiological characteristics of the population, genetic heterogeneity of the population, genetic unity of the population). Mutations of various types are elementary evolutionary material. Genetic processes in populations. An elementary evolutionary phenomenon.

Elementary factors of evolution. Mutation process. Population waves. Insulation. Genetic-automatic processes. Natural selection.

The formation of adaptations is the result of natural selection. Classification and mechanism of adaptation. The relative nature of adaptations.

Species is the main stage of the evolutionary process. Concept, criteria and structure of the type. Speciation is the result of microevolution. Basic ways and methods

speciation.

Patterns of macroevolution. Evolution of ontogenesis (integrity and stability, embryonication and autonomization of ontogenesis, ontogenesis is the basis of phylogeny). Evolution of phylogenetic groups (forms of phylogeny, main directions of evolution, extinction of groups and its causes). Evolution of organs and functions. Evolutionary progress.

Origin and evolution of man.

4.1. Organic evolution is an objective process

Test tasks

1. One of the proofs of evolution is the unity organic world, in which there are a number of organisms that occupy an intermediate position between large systematic groups,– transitional forms. On the image

4.1 Some of the currently existing transitional forms of organisms are presented. Get to know these organisms and indicate in their structure the signs of different types of organization.

2. The skeleton of the limbs of amphibians, reptiles, birds and mammals, despite quite large differences in appearance limbs and the function they perform, turns out to be constructed similarly (Fig. 4.2). What does the similarity in the structure of limbs that perform very different functions in vertebrates indicate?

Rice. 4.1. Currently existing transitional forms:

1 – horseshoe crab, occupying an intermediate position between modern typical arthropods and fossil trilobites; 2 – peripatus, bearing signs of arthropods and annelids; 3 – euglena, combining the characteristics of animals and plants; 4 - horseshoe crab larva, similar to a trilobite larva; 5

– the crawling ctenophore combines, along with the signs of coelenterates, the signs of flatworms

3. In the structure of almost any organism one can find organs or structures that are relatively underdeveloped and have lost their former significance in the process of phylogenesis - these are vestigial organs. Figure 4.3 shows the rudimentary hind limbs of a python, barely noticeable outgrowths of the rudiments of wings in a kiwi, and the rudiments of the pelvic bones of cetaceans. What do these organs indicate?

Rice. 4.2. Homology of vertebrate forelimbs

(salamander, sea turtle, crocodile, bird, bat, whale, mole, man) homologous parts are indicated by the same letters and numbers

4. Among animals, one of the most striking relict forms is the tuateria - the only representative of an entire subclass of reptiles (Fig. 4.4). It reflects the features of reptiles that lived on Earth in the Mesozoic.

Another well-known relic is the lobe-finned fish Coelacanth, which has been preserved little changed since the Devonian.

5. Fossil transitional forms support the existence of kinship among systematic groups of animals. Complete Table 4.1 with some characteristics of protobirds in comparison with reptiles and true birds.

Rice. 4.3. Examples of vestigial organs (A – python hind limbs;

B – kiwi wing; B – elements of the pelvic girdle of a right whale)

List the transitional forms known to you. Why intermediate forms do not provide sufficient evidence of evolution?

7. Bird embryos at the early stages of embryonic development secrete ammonia as the final product of nitrogen metabolism, at later stages urea, and at the last stages of development - uric acid. Similarly, in frog tadpoles, the end product of metabolism is ammonia, and in adult amphibians,

Caudal vertebrae

Flight ability

Lifestyle

Reproduction

8. The study of the embryonic development of higher terrestrial vertebrates has shown that in them some organs are formed and reach a certain level of development that have no significance in an adult animal, but are quite similar to the organs characterizing adult fish. Look at Figure 4.6 and answer,

O What does the fact of the formation of parts of the gill apparatus in the embryos of terrestrial vertebrates indicate?

9. How can one prove the objectivity of the process of evolution of life on Earth?

Rice. 4.5. Imprints of skeletal bones and feathers of Archeopteryx

10. In front of you is a horse, a mouse, a turtle, a butterfly, a pine tree. What methods can most reliably establish the relationship of these forms?

The genotype is the totality of all the genes of an organism, which are its hereditary basis.

Phenotype is the totality of all signs and properties of an organism that are revealed in the process individual development under these conditions and are the result of the interaction of the genotype with a complex of internal and external environmental factors.

Each biological species has a phenotype unique to it. It is formed in accordance with the hereditary information contained in the genes. However, depending on changes in the external environment, the state of signs varies from organism to organism, resulting in individual differences- variability.

Based on the variability of organisms, genetic diversity of forms appears. A distinction is made between modificational, or phenotypic, and genetic, or mutational variability.

Modifying variability does not cause changes in the genotype; it is associated with the reaction of a given, one and the same genotype to changes in the external environment: under optimal conditions, the maximum capabilities inherent in a given genotype are revealed. Modification variability manifests itself in quantitative and qualitative deviations from the original norm, which are not inherited, but are only adaptive in nature, for example, increased pigmentation of human skin under the influence of ultraviolet rays or the development of the muscular system under the influence of physical exercise, etc.

The degree of variation of a trait in an organism, that is, the limits of modification variability, is called the reaction norm. Thus, the phenotype is formed as a result of the interaction of the genotype and environmental factors. Phenotypic characteristics are not transmitted from parents to offspring, only the reaction norm is inherited, that is, the nature of the response to changes in environmental conditions.

Genetic variability can be combinative and mutational.

Combinative variability arises as a result of the exchange of homologous regions of homologous chromosomes during the process of meiosis, which leads to the formation of new gene associations in the genotype. It arises as a result of three processes: 1) independent divergence of chromosomes during meiosis; 2) their random connection during fertilization; 3) exchange of sections of homologous chromosomes or conjugation. .

Mutational variability (mutations). Mutations are abrupt and stable changes in units of heredity - genes, entailing changes in hereditary characteristics. They necessarily cause changes in the genotype, which are inherited by the offspring and are not associated with crossing and recombination of genes.

There are chromosomal and gene mutations. Chromosomal mutations are associated with changes in the structure of chromosomes. This may be a change in the number of chromosomes that is a multiple or not a multiple of the haploid set (in plants - polyploidy, in humans - heteroploidy). An example of heteroploidy in humans can be Down syndrome (one extra chromosome and 47 chromosomes in the karyotype), Shereshevsky-Turner syndrome (one X chromosome is missing, 45). Such deviations in a person’s karyotype are accompanied by health disorders, mental and physical disorders, decreased vitality, etc.

Gene mutations affect the structure of the gene itself and entail changes in the properties of the body (hemophilia, color blindness, albinism, etc.). Gene mutations occur in both somatic and germ cells.

Mutations that occur in germ cells are inherited. They are called generative mutations. Changes in somatic cells cause somatic mutations that spread to that part of the body that develops from the changed cell. For species that reproduce sexually, they are not significant, for vegetative propagation plants they are important.