Presentation of variability and its types. Patterns of variability: modification and mutational variability
slide 1
"Patterns of variability: modification and mutational variability" 28.01.2013 Lesson topic: The purpose of the lesson: - to form the concept of modification and mutational variability; - consider the mechanism of mutations; - find out the causes of mutations; - to study the main characteristics of mutational variability.slide 2
Variability is the ability of living organisms to acquire new features in the process of ontogenesis. Heredity is the property of all living organisms to transmit their characteristics and properties from generation to generation.
slide 3
slide 4
An example of the modification variability of a person is sunburn, which gradually disappears in winter. Modification variability is not associated with changes in genes, chromosomes or the genotype as a whole and occurs under the influence of environmental factors.
slide 5
Pines of the same population differ from each other, as they develop in different conditions. Relationship between phenotype and genotype
slide 6
Reaction rate Limits of modification variability of any attribute are called the reaction rate. It is not the trait itself that is inherited, but the ability to manifest this trait under certain conditions, or we can say that the norm of the organism's reaction to external conditions is inherited. Maple leaves have different sizes, as heat and light are not evenly distributed.
Slide 7
Main characteristics of modification variability: Modification changes are not passed from generation to generation. Modification changes are manifested in many individuals of the species and depend on the effect of environmental conditions on them. Modification changes are possible only within the limits of the reaction norm, and ultimately they are determined by the genotype.
Slide 8
Genotypic variability is associated with a change in the genotype, is the result of mutations.
Slide 9
The term "mutation" was first proposed in 1901. Dutch scientist Hugo de Vries.
slide 10
Mutations are changes in the genotype that occur under the influence of external and internal environment. The process of occurrence of mutations is called mutagenesis, and the factor causing the mutation is called a mutagen. Mutations Gene mutations are associated with changes in the nucleotide sequence of the DNA molecule. Chromosomal mutations are associated with changes in the structure of chromosomes. Genomic mutations lead to a change in the number of chromosomes.
slide 11
Gene, or point, mutations are a change in the sequence of nucleotides in a DNA molecule. Gene mutations should be considered as the result of "mistakes" that occur in the process of doubling DNA molecules. A gene mutation occurs on average in one in 100,000 gametes. But since the number of genes in the human body is large, almost every individual carries a newly emerged mutation.
slide 12
Albinism Albinism is a congenital absence of pigment in the skin, hair, rainbow and pigment membranes eyes. External manifestations In some forms of albinism, there is a decrease in the intensity of the color of the skin, hair and iris, while in others the color of the latter mainly changes. There may be changes in the retina, various visual disorders may occur, including myopia, hyperopia and astigmatism, as well as increased sensitivity to light and other anomalies. Albino people have a white skin color (which is especially striking in non-Caucasian groups); their hair is white (or they are blond). The frequency of albinos among the peoples of European countries is estimated at about 1 per 20,000 inhabitants. In some other nationalities, albinos are more common. So, when examining 14,292 Negro children in Nigeria, among them there were 5 albinos, which corresponds to a frequency of about 1 in 3,000, and among the Indians of Panama (San Blas Bay), the frequency was 1 in 132.
slide 13
slide 14
Daltonism Daltony zm, color blindness is a hereditary, less often acquired feature of vision, expressed in the inability to distinguish one or more colors. It is named after John Dalton, who first described one of the types of color blindness based on his own sensations, in 1794.
slide 15
slide 16
Hemophilia Hemophilia is a hereditary disease associated with impaired coagulation (the process of blood clotting); with this disease, hemorrhages occur in the joints, muscles and internal organs, both spontaneously and as a result of trauma or surgery. With hemophilia, the risk of death of a patient from a hemorrhage in the brain and other vital organs increases sharply, even with a minor injury. Patients with severe hemophilia are disabled due to frequent hemorrhages in the joints (hemarthrosis) and muscle tissue (hematomas). Men usually suffer from hemophilia, and women are carriers of the diseased gene.
slide 17
Chromosomal mutations are rearrangements of chromosomes. A deletion is the loss of a section of a chromosome. A duplication is a doubling of a portion of a chromosome. An inversion is a 180° rotation of a segment of a chromosome. Translocation is the exchange of segments of non-homologous chromosomes. Fusion of two non-homologous chromosomes into one.
slide 18
slide 19
slide 20
A disease caused by an anomaly of the chromosome set (a change in the number or structure of autosomes), the main manifestations of which are mental retardation, a peculiar appearance of the patient and congenital malformations. One of the most common chromosomal diseases, occurs on average with a frequency of 1 in 700 newborns. Down's disease
slide 21
Down syndrome In boys and girls, the disease occurs equally often. Children with Down syndrome are more likely to be born to older parents. If the mother's age is 35-46 years, then the probability of having a sick child increases to 4.1%, with the age of the mother, the risk increases. The chance of recurrence in a family with trisomy 21 is 1-2%.
slide 22
Klinefelter's syndrome Klinefelter's syndrome occurs in 1 in 500 boys. The extra X chromosome is inherited from the mother in 60% of cases, especially during late pregnancy. The risk of inheriting the paternal chromosome does not depend on the age of the father. Klinefelter's syndrome is characterized by the following features: tall stature, disproportionately long legs. Violations in the development of the genital organs are found in puberty and later. Patients are usually infertile.
slide 23
45 xr. - XO The height of adult patients is 20-30 cm below the average. Treatment of patients with this syndrome is complex and includes reconstructive and plastic surgery, hormonal therapy (estrogen, growth hormone), psychotherapy.
slide 24
Shereshevsky-Turner syndrome Shereshevsky-Turner syndrome is the only form of monosomy in live births. Clinically, Shereshevsky-Turner syndrome is manifested by the following symptoms. Underdevelopment of the genital organs or their absence. There are various malformations of the cardiovascular system and kidneys. There is no decrease in intelligence, but patients show emotional instability. Appearance patients are peculiar. Characteristic symptoms are noted: a short neck with excess skin and pterygoid folds; in adolescence, a lag in growth and development of secondary sexual characteristics is revealed; adults are characterized by skeletal disorders, low position of the auricles, body disproportions (shortening of the legs, relatively wide shoulder girdle, narrow pelvis).
Description of the presentation on individual slides:
1 slide
Description of the slide:
Topic: "Modification variability" Koshedova Anna Ivanovna Tasks: To characterize non-hereditary variability
2 slide
Description of the slide:
Variability Genetics studies not only heredity, but also the variability of organisms. Variability is the ability of living organisms to acquire new features and properties. Due to variability, organisms can adapt to changing environmental conditions. There are two types of variability: Non-hereditary, or phenotypic, - variability in which no changes in the genotype occur. It is also called group, specific, modification. Hereditary, or genotypic, individual, indefinite - changes in the characteristics of an organism due to a change in the genotype; it happens: combinative - resulting from the recombination of chromosomes in the process of sexual reproduction and sections of chromosomes in the process of crossing over; mutational - resulting from a sudden change in the state of genes;
3 slide
Description of the slide:
4 slide
Description of the slide:
5 slide
Description of the slide:
White hare in summer and winter. Variability? Modification, the genotype does not change. The ermine rabbit remains white at elevated temperatures. Variability? Modification, the genotype does not change.
6 slide
Description of the slide:
7 slide
Description of the slide:
Modification variability An important role in the formation of signs of organisms is played by its habitat. Each organism develops and lives in a certain environment, experiencing the action of its factors that can change the morphological and physiological properties of organisms, i.e. their phenotype. A classic example of the variability of traits under the influence of environmental factors is the heterogeneity of the arrowhead: the leaves immersed in water are ribbon-shaped, the leaves floating on the surface of the water are rounded, and those in the air are arrow-shaped. If the whole plant is completely immersed in water, its leaves are only ribbon-like.
8 slide
Description of the slide:
Modification variability Under the influence of ultraviolet rays in people (if they are not albinos), a tan occurs as a result of the accumulation of melanin in the skin, and in different people the intensity of skin color is different. Thus, changes in a number of characteristics of organisms are caused by the action of environmental factors. And these changes are not inherited. So, if you get offspring from newts grown on dark soil and place them on light soil, then they will all have a light color, and not dark, like their parents. I.e, this species variability does not affect the genotype and therefore is not transmitted to descendants.
9 slide
Description of the slide:
10 slide
Description of the slide:
Modification variability The variability of organisms that occurs under the influence of environmental factors and does not affect the genotype is called modification. Modification variability is of a group nature, that is, all individuals of the same species, placed in the same conditions, acquire similar characteristics. For example, if a vessel with green euglenas is placed in darkness, then all of them will lose their green color, but if they are again exposed to light, they will all become green again. Modification variability is definite, that is, it always corresponds to the factors that cause it. So, ultraviolet rays change the color of human skin, increased physical activity affects the degree of muscle development.
11 slide
Description of the slide:
Modification variability Non-adaptive modifications: morphoses and phenocopies. Morphoses are non-hereditary changes caused by extreme or unusual environmental factors (X-ray morphosis, chemomorphosis) that change somatic cells. Morphoses are considered as "deformities" that are not inherited and are not adaptive. For example, when larvae of Drosophila are irradiated, adults with clippings in various parts of the wing are obtained, which are the result of the death of part of the cells of the imaginal wing discs due to irradiation. Phenocopies are non-hereditary changes similar to known mutations. Phenocopies are the result of the action of physical and chemical agents on a genetically normal organism. For example, when using thalidomide, children were often born with fecomelia - shortened flipper-shaped hands, which can also be caused by mutant alleles.
12 slide
Description of the slide:
Modification variability Despite the fact that under the influence of environmental conditions, signs can change, this variability is not unlimited. So, on a wheat field, you can find plants with large ears (20 cm or more) and very small ones (3-4 cm). This is explained by the fact that the genotype defines certain boundaries within which a trait change can occur. The degree of variation of a trait, or the limits of modification variability, is called the reaction norm.
13 slide
Description of the slide:
14 slide
Description of the slide:
Modification variability As a rule, quantitative traits (plant height, yield, leaf size, milk yield of cows, chicken egg production) have a wider reaction rate, that is, they can vary over a wide range than qualitative traits (wool color, milk fat content, flower structure, group blood). Knowledge of the reaction rate is of great importance for practice Agriculture Thus, modification variability is characterized by the following main properties: 1. Non-heritability; 2. Group character of changes; 3. Correspondence of changes to the action of the environmental factor.
15 slide
Description of the slide:
Modification variability To assess the severity of the studied trait, the following concept is used: EXPRESSIVENESS - the degree of phenotypic manifestation of a gene. This indicator depends on the interaction of the gene with other genes, or on the impact of external conditions. The presence of a given gene does not always mean that it will appear in the phenotype. To estimate the number of individuals in which this trait is phenotypically manifested, the term PENETRATION is used. Penetrance is the frequency of the phenotypic manifestation of a trait in individuals with the same genotype for this gene. The penetrance of congenital dislocation of the hip is, for example, 20%, in diabetes mellitus - 65%.
16 slide
Description of the slide:
Modification variability Statistical patterns of modification variability. The modification variability of many traits of plants, animals, and humans follows general patterns. These patterns are revealed on the basis of the analysis of the manifestation of the trait in a group of individuals (n). The degree of expression of the studied trait among the members of the sample is different. Each specific value of the studied attribute is called a variant and is denoted by the letter v. When studying the variability of a trait in a sample population, a variation series is compiled in which individuals are arranged in ascending order of the indicator of the trait under study.
17 slide
Description of the slide:
Modification variability Based on the variation series, a variation curve is constructed - a graphical display of the frequency of occurrence of each variant. The frequency of occurrence of individual variant is denoted by the letter p. For example, if you take 100 ears of wheat (n) and count the number of ears in an ear, then this number will be from 14 to 20 - this is the numerical value of option (v). Variation series: v = 14 15 16 17 18 19 20 The frequency of occurrence of each variant p = 2 7 22 32 24 8 5 The average value of the trait occurs more often, and variations that differ significantly from it are much less common. This is called the normal distribution. The curve on the graph is usually symmetrical. Variations, both greater than average and lesser, occur with equal frequency.
18 slide
Description of the slide:
Modification variability It is easy to calculate the average value of this trait. To do this, use the formula: (vּp) M = n where M - average value sign, in the numerator the sum of the products of the variant by their frequency of occurrence, in the denominator - the number of variant. For this feature, the average value is 17.13. Knowledge of the patterns of modification variability is of great practical importance, since it makes it possible to foresee and plan in advance the degree of manifestation of many features of organisms depending on environmental conditions.
19 slide
Description of the slide:
Repetition Modification variability Characteristic Can it be considered a certain variability? Can it be considered group variability? Impact on the genotype? Effect on the phenotype? Inheritance of received changes? Significance for the organism: Significance for evolution.
1 slide
Topic: "Modification variability" Pimenov A.V. Tasks: Describe non-hereditary variability
2 slide
Variability Genetics studies not only heredity, but also the variability of organisms. Variability is the ability of living organisms to acquire new features and properties. Due to variability, organisms can adapt to changing environmental conditions. There are two types of variability: Non-hereditary, or phenotypic, - variability in which no changes in the genotype occur. It is also called group, specific, modification. Hereditary, or genotypic, individual, indefinite - changes in the characteristics of an organism due to a change in the genotype; it happens: combinative - resulting from the recombination of chromosomes in the process of sexual reproduction and sections of chromosomes in the process of crossing over; mutational - resulting from a sudden change in the state of genes;
3 slide
4 slide
5 slide
White hare in summer and winter. Variability? Modification, the genotype does not change. The ermine rabbit remains white at elevated temperatures. Variability? Modification, the genotype does not change.
6 slide
7 slide
Modification variability An important role in the formation of signs of organisms is played by its habitat. Each organism develops and lives in a certain environment, experiencing the action of its factors that can change the morphological and physiological properties of organisms, i.e. their phenotype. A classic example of the variability of traits under the influence of environmental factors is the heterogeneity of the arrowhead: the leaves immersed in water are ribbon-shaped, the leaves floating on the surface of the water are rounded, and those in the air are arrow-shaped. If the whole plant is completely immersed in water, its leaves are only ribbon-like.
8 slide
Modification variability Under the influence of ultraviolet rays in people (if they are not albinos), a tan occurs as a result of the accumulation of melanin in the skin, and in different people the intensity of skin color is different. Thus, changes in a number of characteristics of organisms are caused by the action of environmental factors. And these changes are not inherited. So, if you get offspring from newts grown on dark soil and place them on light soil, then they will all have a light color, and not dark, like their parents. That is, this type of variability does not affect the genotype and therefore is not transmitted to descendants.
9 slide
10 slide
Modification variability The variability of organisms that occurs under the influence of environmental factors and does not affect the genotype is called modification. Modification variability is of a group nature, that is, all individuals of the same species, placed in the same conditions, acquire similar characteristics. For example, if a vessel with green euglenas is placed in darkness, then all of them will lose their green color, but if they are again exposed to light, they will all become green again. Modification variability is definite, that is, it always corresponds to the factors that cause it. So, ultraviolet rays change the color of human skin, increased physical activity affects the degree of muscle development.
11 slide
Modification variability Non-adaptive modifications: morphoses and phenocopies. Morphoses are non-hereditary changes caused by extreme or unusual environmental factors (X-ray morphosis, chemomorphosis) that change somatic cells. Morphoses are considered as "deformities" that are not inherited and are not adaptive. For example, when larvae of Drosophila are irradiated, adults with clippings in various parts of the wing are obtained, which are the result of the death of part of the cells of the imaginal wing discs due to irradiation. Phenocopies are non-hereditary changes similar to known mutations. Phenocopies are the result of the action of physical and chemical agents on a genetically normal organism. For example, when using thalidomide, children were often born with fecomelia - shortened flipper-shaped hands, which can also be caused by mutant alleles.
12 slide
Modification variability Despite the fact that under the influence of environmental conditions, signs can change, this variability is not unlimited. So, on a wheat field, you can find plants with large ears (20 cm or more) and very small ones (3-4 cm). This is explained by the fact that the genotype defines certain boundaries within which a trait change can occur. The degree of variation of a trait, or the limits of modification variability, is called the reaction norm.
13 slide
14 slide
Modification variability As a rule, quantitative traits (plant height, yield, leaf size, milk yield of cows, chicken egg production) have a wider reaction rate, that is, they can vary over a wide range than qualitative traits (wool color, milk fat content, flower structure, group blood). Knowledge of the reaction rate is of great importance for the practice of agriculture. Thus, the modification variability is characterized by the following main properties: 1. Non-heritability; 2. Group character of changes; 3. Correspondence of changes to the action of the environmental factor.
15 slide
Modification variability To assess the severity of the studied trait, the following concept is used: EXPRESSIVENESS - the degree of phenotypic manifestation of a gene. This indicator depends on the interaction of the gene with other genes, or on the impact of external conditions. The presence of a given gene does not always mean that it will appear in the phenotype. To estimate the number of individuals in which this trait is phenotypically manifested, the term PENETRATION is used. Penetrance is the frequency of the phenotypic manifestation of a trait in individuals with the same genotype for this gene. The penetrance of congenital dislocation of the hip is, for example, 20%, in diabetes mellitus - 65%.
16 slide
Modification variability Statistical patterns of modification variability. The modification variability of many traits of plants, animals, and humans follows general patterns. These patterns are revealed on the basis of the analysis of the manifestation of the trait in a group of individuals (n). The degree of expression of the studied trait among the members of the sample is different. Each specific value of the studied attribute is called a variant and is denoted by the letter v. When studying the variability of a trait in a sample population, a variation series is compiled in which individuals are arranged in ascending order of the indicator of the trait under study.
17 slide
Modification variability Based on the variation series, a variation curve is constructed - a graphical display of the frequency of occurrence of each variant. The frequency of occurrence of individual variant is denoted by the letter p. For example, if you take 100 ears of wheat (n) and count the number of ears in an ear, then this number will be from 14 to 20 - this is the numerical value of option (v). Variation series: v = 14 15 16 17 18 19 20 The frequency of occurrence of each variant p = 2 7 22 32 24 8 5 The average value of the trait occurs more often, and variations that differ significantly from it are much less common. This is called the normal distribution. The curve on the graph is usually symmetrical. Variations, both greater than average and lesser, occur with equal frequency.
18 slide
Modification variability It is easy to calculate the average value of this trait. To do this, use the formula: (v p) M \u003d n where M is the average value of the sign, in the numerator the sum of the products of the variant by their frequency of occurrence, in the denominator - the number of variant. For this feature, the average value is 17.13. Knowledge of the patterns of modification variability is of great practical importance, since it makes it possible to foresee and plan in advance the degree of manifestation of many features of organisms depending on environmental conditions.
Variability Hereditary (genotypic) Hereditary (genotypic) Phenotypic 2 Mutational (hereditary, indeterminate, individual). Correlative. Combinative (variability arising by crossing). Non-hereditary definite, group
6
Types of phenotypic variability Modifications are non-hereditary changes in the genotype that occur under the influence of an environmental factor, are adaptive in nature and most often reversible (for example: an increase in red blood cells in the absence of oxygen). Morphoses are non-hereditary changes in the phenotype that occur under the influence of extreme environmental factors, are not adaptive in nature and are irreversible (for example: burns, scars). 12 Phenocopies are a non-hereditary change in the genotype that resembles hereditary diseases (enlargement of the thyroid gland in an area where there is not enough iodine in the water or land).
15
Construction of a variation curve is the average value of the severity of the trait where M is the average value, V is the variant, P is the frequency of occurrence of the variant, n is the total number of variants of the variation series. 16 The variation curve is a graphic representation of the relationship between the range of variability of a trait and the frequency of occurrence of individual variants of this trait.
Variation series The variation series represents a series of variants (values of a trait) arranged in descending or ascending order 17 (for example: if you collect leaves from the same tree and arrange them as the length of the leaf blade increases, then you get a variation series of variability of this trait).
Combinative variability is variability based on the formation of recombinations, i.e. such combinations of genes that the parents did not have. 20 Combinative variability is based on the sexual reproduction of organisms, as a result of which a huge variety of genotypes arises.
Sources of genetic variability Independent divergence of homologous chromosomes in the first meiotic division. Mutual exchange of sections of homologous chromosomes, or crossing over. Recombinant chromosomes, once in the zygote, contribute to the appearance of signs that are atypical for each of the parents. Random combination of gametes during fertilization. 22
Mutation theory Mutations arise suddenly, abruptly, as discrete changes in traits. These are qualitative changes that are passed down from generation to generation. Mutations manifest themselves in different ways and can be both beneficial and harmful. The probability of detecting mutations depends on the number of individuals studied. Similar mutations can occur repeatedly. Mutations are undirected (spontaneous), that is, any part of the chromosome can mutate. 24 G. De Vries in the years.
Classification of mutations: 25 Gene (change in the structure of the gene) - change in DNA - violation of the order of nucleotides Genomic (change in the number of chromosomes in the karyotype) - euploidy - aneuploidy: * trisomy * monosomy Chromosomal (change in the structure of chromosomes) - loss of a section of chromosomes - Doubling of a fragment of chromosomes - rotation parts of chromosomes per 180* Mutations 1. By the nature of the change in the genome
They occur when there is damage or disturbance in the order or replacement of nucleotides, the appearance of an internal duplication or deletion in the DNA molecule. These changes in individual genes often lead to severe degenerative diseases, in particular, numerous metabolic diseases due to impaired synthesis of proteins and enzymes. Gene mutations
A hereditary disease that leads to the death of children and adolescents. Instead of normal hemoglobin A, erythrocytes contain abnormal hemoglobin S. The anomaly is caused by a mutation in the sixth nucleotide triplet of the hemoglobin gene DNA, which leads to the replacement of glutamic (GLU) acid in the alpha chain of the hemoglobin protein with valine (VAL). 27 Sickle cell anemia (KLU) (SAL)
28 Hereditary disease found in one of the newborns. The disease is characterized by a pronounced mental retardation, which develops as a result of a violation of normal biochemical processes in the brain due to the accumulation of phenylalanine in the body. Phenylketonuria Gene Mutations
34 Generative (in germ cells) Detected only in the next generation Generative (in germ cells) Detected only in the next generation Somatic (in body cells) Manifested in a given organism and not transmitted to offspring during sexual reproduction Somatic (in body cells) Manifested in a given organism and are not transmitted to offspring during sexual reproduction Classification of mutations: 2. According to the place of occurrence:
Spontaneous Under natural conditions Under the influence of mutagenic factors Without human intervention Are the source material for natural selection Induced Under the directed action of a mutagenic factor With Human intervention Is the source material for artificial selection 37 Classification of mutations: 5. For reasons:
The law of homological series in hereditary variability Species and genera that are genetically similar are characterized by similar series of hereditary variability with such regularity that knowing a number of forms within one species, one can predict the presence of the same forms in other genera and species. N.I. Vavilov, 1920
Variability
slide 2
Variability is the ability of living organisms to acquire new features and properties. Due to variability, organisms can adapt to changing environmental conditions.
slide 3
slide 4
There are two types of variability: Non-hereditary, or phenotypic, - variability in which no changes in the genotype occur. It is also called group, specific, modification. Hereditary, or genotypic, individual, indefinite - changes in the characteristics of an organism due to a change in the genotype; it happens: combinative - resulting from the recombination of chromosomes in the process of sexual reproduction and sections of chromosomes in the process of crossing over; mutational - resulting from a sudden change in the state of genes;
Slide 5: Modification variability - variability of organisms that occurs under the influence of environmental factors and does not affect the genotype
Patterns of variability Modification variability is the variability of organisms that occurs under the influence of environmental factors and does not affect the genotype. A change that is not hereditary is not essential to us. Charles Darwin
Slide 6: Signs of the body
quality (they can be described): coloring (color); the form; blood type; fat content of milk, etc. quantitative (they can be measured): length (height); weight; volume; number of seeds, etc.
Slide 7
What signs (qualitative or quantitative) are more subject to variability? Will these changes show up in the next generations? Why? Is the degree of variability of a trait the same for all individuals of a given species? Why?
Slide 8: Qualitative and quantitative features: qualitative - established in a descriptive way: - color of animals, color of seeds, growth. Less affected by the environment. Quantitative determined by measurement: - yield of agricultural crops, milk yield of cows, egg production of chickens. more affected by the environment
Slide 9
The limits of the modification variability of a trait are called its reaction norm. The reaction norm is an inherited trait.
10
Slide 10: A strange object grows on the river, The water will twist the lower leaves, The middle one will lay it on the water like a raft, The upper one will slide like an arrow to the sky
11
slide 11
Patterns of variability One and the same genotype can give a different value of a trait under different conditions. Some signs have a wide reaction rate, while others have a much narrower one. The arrow leaf has two types of leaves: - underwater surface The main factor responsible for the development of the shape of the leaves is the degree of illumination. ! Give examples of traits with narrow and wide reaction norms.
12
slide 12
Modification variability As a rule, quantitative traits (plant height, yield, leaf size, milk yield of cows, chicken egg production) have a wider reaction rate, that is, they can vary over a wide range than qualitative traits (wool color, milk fat content, flower structure, group blood). Knowledge of the reaction rate is of great importance for the practice of agriculture. Thus, the modification variability is characterized by the following main properties: 1. Non-heritability; 2. Group character of changes; 3. Correspondence of changes to the action of the environmental factor.
13
slide 13
Statistical patterns of modification variability. The modification variability of many traits of plants, animals, and humans follows general patterns. These patterns are revealed on the basis of the analysis of the manifestation of the trait in a group of individuals (n). The degree of expression of the studied trait among the members of the sample is different. Each specific value of the studied attribute is called a variant and is denoted by the letter v. When studying the variability of a trait in a sample population, a variation series is compiled in which individuals are arranged in ascending order of the indicator of the trait under study.
14
Slide 14
Based on the variation series, a variation curve is constructed - a graphical display of the frequency of occurrence of each variant. The frequency of occurrence of individual variant is denoted by the letter p. For example, if you take 100 ears of wheat (n) and count the number of ears in an ear, then this number will be from 14 to 20 - this is the numerical value of option (v). Variation series: v = 14 15 16 17 18 19 20 The frequency of occurrence of each variant p = 2 7 22 32 24 8 5 The average value of the trait occurs more often, and variations that differ significantly from it are much less common. This is called the normal distribution. The curve on the graph is usually symmetrical. Variations, both greater than average and lesser, occur with equal frequency.
15
slide 15
It is easy to calculate the average value of this feature. To do this, use the formula: (v ּ p) M = n where M is the average value of the feature, the numerator is the sum of the products of the variant by their frequency of occurrence, and the denominator is the number of variant. For this feature, the average value is 17.13. Knowledge of the patterns of modification variability is of great practical importance, since it makes it possible to foresee and plan in advance the degree of manifestation of many features of organisms depending on environmental conditions.
16
Slide 16: Patterns of variability
Hereditary Non-hereditary Change in the genotype Change in the phenotype Inherited Not inherited Individual Mass Independent, harmful or useful Adaptive Not adequate to the environment Adequate to the environment Leads to the formation of combinations and mutations Leads to the formation of modifications Causes - ionizing radiation, toxic substances, etc. Causes - climatic, food, etc. changes
17
Slide 17: Combination hereditary variability
Possible combinations: Prophase I of meiosis - crossing over; Anaphase I - independent divergence of homologous chromosomes; Anaphase II - independent chromatid separation Random fusion of gametes
18
Slide 18: CONCLUSIONS:
Patterns of variability CONCLUSIONS: Variability is manifested in all organisms and is their property. There are hereditary and non-hereditary (modification) variability. The limits of the modification variability of a trait are called the reaction norm. Modifications (modification changes) do not affect the genotype; are not inherited; arise under the influence of environmental factors; appear in a similar way in many individuals of the species; may disappear over time. Possible only within the limits of the reaction norm, i.e. determined by genotype. It is not the trait itself that is inherited, but the ability to manifest this trait under certain conditions, i.e. the rate of reaction of the organism to external conditions is inherited.
Popular
- Principles and criteria for the examination of the value of documents
- Three Siemens NX Success Stories The integrated system is the ideal solution
- Basic elements of personnel management Basic elements of personnel management
- Quality management at the enterprise: standards, stages of implementation, tips
- How is the quarterly bonus calculated and how is it paid?
- Mysterious crossing on Abbey Road in England John Lennon originally named the group differently
- "Abbey Road" cover as the basis for a conspiracy legend
- How to write a letter of guarantee?
- Merchandising, its types and principles Fundamentals of merchandising in the textile industry
- Marketing activities in wholesale and retail trade