Along with the population in genetics there is a concept "Clean line" is the offspring, obtained only from one parent and having a complete similarity of genotype with it.
Clean lines can be created in crop production in self-polishing plants. In contrast to populations, they are characterized by complete homosigitia. Due to the complete homozygousness, the selection in the pure line is not possible, since all individuals entering it have an identical set of genes. High-consumption linear mice, rats and other laboratory animals are created in order to conduct various experiments, for example, to test for mutagenity of certain drugs, evaluations of vaccines, etc.
The population consists of animals of different genotypes. The selection efficiency in it depends on the degree of genetic variability - the ratio of dominant and recessive genes. Hardy and Weinberg conducted a mathematical analysis of the distribution of genes in large populations, where there is no selection, mutations and mixing populations. They found that such a population is in a state of equilibrium at the ratio of genotypes, which is determined by the formula
p2aa + + ipqaa + q) aa \u003d 1,
where p is the frequency of the dominant gene A,
q is the frequency of his recessive allele a.
In accordance with this, the law, or the rule, Hardy - Weinberg, according to which, in the absence of factors that change the frequencies of genes, populations, with any ratio of alleles from generation to generation, retain these frequencies of alleles permanent. Despite the known limitations, according to the Hardy - Weinberg formula, it is possible to calculate the population structure and determine the frequencies of heterozygotes (for example, by lethal or sublotheal genes, knowing the homozygot frequencies on recessive features and frequencies of individuals with a dominant sign), to analyze shifts in gene frequencies on specific features in A result of selection, mutations and other factors.
The population is in equilibrium only when it does not take place. When selecting individual animals in such a population, the GATIS ratio changes, which affects the genetic structure of the next generation. However, K. Pearson showed that as soon as the state of the pamctions (free crossing), the ratio of genotypes and phenotypes in the population in the next generation returns to the one that corresponds to the Hard - Weinberg formula, but with a different ratio. Crossing, restoring the ratio of genotypes in the population, in accordance with the Formula of Hardy - Weinberg received the name of the stabilizing. From this it follows the conclusion: when used in the population of random, indispensable producers or the diet, it is observed stabilization of signs of productivity at the same level, and an increase in animal productivity in such a situation is impossible. In the same way, in the absence of brave of heterozygous carriers of recessive anomalies, the frequency of manifestation of abnormal animals in the population remains unchanged.
In populations of farm animals, the frequencies of genes are constantly changing, which can be observed when analyzing adjacent generations. Such changes constitute the essence of genetic evolution. The main factors of evolution: mutations, natural and artificial selection, migration, gene drift.
One of the main causes of genetic variability in the population is mutations. Spontaneous mutations of each gene occur with a low frequency, but the total frequency of mutations of all genes that contain populations is very large. Mutations arising in the genital cells of the parent generation lead to a change in the genetic structure in offspring. In the population of a constant number in the absence of selection, most of the mutations arising quickly lost, but some of them may be preserved in a number of generations. The disappearance of mutant genes from the population opposes the effect of the mutational process, as a result of which repeated mutations are formed.
The genetic structure of populations is formed and varies under the action of natural and artificial selection. The effect of natural selection is that the preferential reproduction has individuals with high viability, strength, fertility, etc., i.e., more adapted to environmental conditions. In case of artificial selection, signs of productivity are determining.
IN AND. Vlasov notes that natural selection It goes at all stages of ontogenesis of the population - from the formation of Games to an adult organism. At the same time, it significantly affects the pace of artificial selection due to the opposite action during breeding to a high level of development of productive signs, unknown species biological boundaries. Based on this, in the selection of animals, it is necessary to take into account not only productive features, but also signs of fitness to environmental conditions.
By S.M. Gershenzon, the intensity criterion of the natural selection is the difference in the adaptability of the compared groups, called the selection coefficient and expressed in the fractions of the unit. For example, if the probability of leaving the offspring individuals with an AA genotype is 10% less than individuals with an AA or AA genotype, then the adaptation of these groups for individuals AA and AA is 1 for individuals AA - 0.9.
From the point of view of veterinary genetics, the effectiveness of selection against harmful mutations is important, primarily a recessive type. The analysis shows that high frequencies of a recessive mutant gene by selection can be quickly reduced to low values. To reduce the frequency of the death gene, for example from 0.3 to 0.2, there are enough two generations.
The frequency of homozygotes (AA) on the mutant gene depends on the frequency of heterozygous animals in the population. The identification of these heterozygotes and elimination of them accordingly will reduce the frequency of genetic anomalies caused by the mutant genome, which is especially important at high frequency of mutations.
The genetic structure of the population may change by virtue of random genetic and automatic processes (by N.P. Dubinin) or gene drift (according to S. Wright). Observations show that the most intensive drift of genes proceeds in small populations. For example, there are cases of high concentration of rare mutations in small isolated populations of cattle and other animal species associated, obviously with genetic and automatic processes. The spread of mutations in different populations of animals may occur as a result of migrations.
Pairing animals in related relationships is called inbreeding. Related pairing, or inbreeding, - the selection method used in breeding animal husbandry to consolidate the valuable hereditary signs of a particular animal in subsequent generations. Related animals have resemblance to certain pairs of alleles, which they received from the general ancestor. This similarity is the greater, the closer the degree of kinship.
Each animal in the genotype has allelic genes, both in homozygous and in heterozygous state. In the heterosigote, harmful mutant recessive genes are usually located. In tyrim increases the likelihood of the merger of identical heats, carrying mutant genes in the heterozygous state, and transition them to a homozygous state. This probability is proportional to the degree of kinship of the flooded animals.
Thus, as a result of the use of inbreeding, a change in gene frequencies occurs, the likelihood of recovery of recessive homozigot increases, which causes the inbred depression expressed in reducing the viability, animal fertility, the birth of anomalous individuals.
Inbreeding, as a rule, was complex - simultaneously on two (1st digit) or three (2nd digit) ancestors.
Immissive depression in terms of indicators characterizing the productivity and viability of animals is not a fatal satellite of a related pairing.
There are many examples of when injecting different degrees, including similar, negative consequences were not observed.
N.P. The Dubinin notes in this regard that "the line deteriorates until the processes of consistent accumulation of harmful recessive genes passing into a homozygous state. When it comes a more or less pronounced completion of this process, the lines in their properties become relatively constant and can be maintained in such a stable state. Change the genotype of such lines can only new mutations accumulating in them. " However, the academician emphasizes, "many lines in inbreeding, of course, are dying, because lethal and half-liter genes are transferred to the homozygous state." Therefore, inbreeding is used as a method of individual selection for transfer to the homozygous state of valuable genes of outstanding animals.
During the long-term evolution of animals, along with useful mutations, pickled selection, a certain range of gene and chromosomal mutations has accumulated in populations or rocks. Each generation of the population inherits this cargo of mutations, and in each of them new mutations arise, some of which are transmitted to subsequent generations.
Obviously, most of harmful mutations are noted by natural selection or eliminated in the breeding process. These are primarily dominant gene mutations, phenotypically manifested in heterozygous state, and quantitative changes in chromosome sets. Recessively active gene mutations in heterozygous state and structural perestroika chromosomes, noticeably affecting the viability of their carriers, can pass through the sieve of selection. They form the genetic cargo of the population. Thus, under the genetic cargo of the population, the combination of harmful genes and chromosomal mutations is understood. There are mutational and segregation genetic goods. The first is formed due to new mutations, the second - as a result of splitting and reconnecting alleles when crossing heterozygous carriers of "old" mutations.
The frequency of death, semi-liter and sub-vending generations transmitted from generation to generation in the form of a mutational genetic cargo due to the difficulty of identifying carriers are not accurately accountable. Morton and Crowe proposed the form of calculating the level of genetic cargo in the amount of lethal equivalents. One lethal equivalent corresponds to one lethal gene due to mortality with a 10% probability, two lethal genes at a 50% probability of death, etc. The magnitude of the genetic cargo by the Morton formula:
log es \u003d a + bf,
where S is a part of the offspring remaining alive;
A - mortality measured by lethal equivalent in the population under the condition of random pairing (F \u003d 0), plus mortality due to external factors;
- expected increase in mortality when the population becomes completely homozygous (F \u003d 1);
F - the inbreeding coefficient.
The level of genetic cargo can be determined on the basis of the phenotypic manifestation of mutations (deformities, congenital exchanging anomalies, etc.), analysis of the type of their inheritance, frequency in the population.
N.P. Dubinin proposes to determine the genetic cargo of the population by comparing the frequencies of stillborn in related and unrelated seats of parental pairs. It should be borne in mind that at a high frequency of heterozygotes on recessive lethal and semi-fat mutant genes, the birth of animals with anomalies should not necessarily be due to the inbreeding of close and moderate degrees. The overall ancestor (the source of mutation) may be in distant rows of pedigree. For example, the bull of the Trumor 2918 is a heterozygous carrier of a mutant recessive gene, was in V, VI, VII of the ranks of the ancestors in the state farm "Red Baltika", but when using its Rights of the automaton 1597, there were mass cases of the birth of murderous calves.
These data to a certain extent characterize the levels of genetic cargo on individual mutant genes in specific cattle populations.
Chromosomal mutations are an integral part of the genetic cargo. Their accounting is conducted by a direct cytological method. According to the results of numerous studies, the main component of the cargo of aberration chromosomes in cattle are Robertson translocations, and in pigs - reciprocal. The most common mutation in cattle was 1/29 chromosome translocation. The scope of the variability of the frequency of this aberration, according to our data, in populations of paveo-motley cattle ranged from 5 to 26%.
Thus, the concept of genetic cargo in the light of modern achievements of cytogenetics should be expanded. Now, when a wide spectrum of aberration chromosomes is known and strict inheritance of individuals (translocations and inversion) is established, it seems appropriate to take them into account along with harmful gene mutations as a component of the genetic cargo.
The existence in populations of hereditary variability, first of all mutations in heterozygous state, allows them to quickly adapt to new environmental conditions due to changes in the genetic structure. The mutational process also leads to the formation of a genetic polymorphism population - a variety of frequencies of alleles, homozygotes on dominant, heterozygot or homozygotes on recessive genes. Polymorphism is a mechanism supporting the existence of populations. If, for example, heterozygility provides better adaptability to the changed environmental conditions, then selection in favor of heterozygot, which leads to a balanced polymorphism - reproducing in a population from generation to generation of a certain ratio of various genotypes and phenotypes. The processes that ensure the ability of the population to preserve their genetic structure are called genetic homeostasis.
In genetics, two classes of signs are distinguished - high-quality and quantitative. They differ in the nature of the variability and characteristics of inheritance. Qualitative features are characterized by intermittent, and quantitative - continuous variability. The first of them give clear boundaries when splitting on dominant or recessive signs. This is due to the fact that each of them is usually controlled by one allelic genome. Quantitative signs do not give clear boundaries of splitting with different embodiments, although they differ from a higher degree of variability. A feature of quantitative signs is the complex nature of inheritance. Each of them is determined not by one, but a variety of loci in chromosomes. Such a type of inheritance, when one sign is determined by many genes, is called polygenic. The level of development of the quantitative feature depends on the ratio of dominant and recessive genes, other genetic factors and the degree of modifying the effects of the external environment. The variability in the quantitative basis in the population is made up of genetic and paraloch (external) variability.
The concept of inheritance of signs and the coefficient of inheree. Different quantitative features have an unequal degree of genetic variability, and the conditions of the external environment have a different impact on the level of the phenotypic manifestation of one or another feature. When the animals are selected, the knowledge of the extent will the coincidence of the levels of the development of a quantitative basis for parents and offspring or to what the descendants will inherit quantitative economic signs or pathological signs of parents.
Economic features include milkness, fat content and protein in the milk of cows, Nastrig wool in sheep, egg production in chickens, the increase in live weight, fertility, etc. Increasing the level of development of economic traits is achieved by the constant selection of the best individuals for reproduction. The effectiveness of the selection on these features depends on the degree of their inheritance, the relationship between them, the difference between the average sign of the selected group and the average for the herd (selection differential) and the interval between generations.
The values \u200b\u200bof the inheritance coefficients depend on the nature of the feature. So, the average value of A2 according to the fun is 0.25, the fatomarity - 0.38, the live weight of the sheep - 0.35, the exit of pure wool - 0.55, fertility in cattle - 0.08, etc.
Selective practice and special studies have accumulated data that indicating that in some cases the level of development of one or more signs in the offspring exceeds the severity of these signs from the best of parents. Such a phenomenon called heterosis does not fit into the usual framework of inheritance. To explain it, various hypotheses are proposed:
1) a heterozygous state for many genes;
2) the interaction of dominant favorable genes;
3) Supermination, when heterozygotes are superior to homozygotes.
N.V. Turbin proposed the theory of genetic balance, which is based on the complex nature of the causal relationship between hereditary factors and signs.
N.G. Dmitriev and I.ji. Halperin notes that the main cause of heterosis should be sought in the peculiarities of the evolution of the species, rock, lines. It should be borne in mind that everything in nature is aimed at preserving life. The manifestation of heterosise depends on the genetic nature of the feature. Thus, with an intergenerate or interlinear crossing, heterosis is more manifested in terms of signs having a low degree of inheritability
As for signs having an average or high inheritability, heterosis on them is most often manifested, and the hybrids are usually intermediate.
In the presence of true heterosis, the magnitude of the index or more than 100%. If the magnitude of the heterosis is less than 100% or has a "minus" sign, then it is more correct to talk about the best or worse combination ability of lines. Crossing the latter according to a certain scheme provides a better development of one character from the father in a hybrid offspring, and the other from the mother, although this sign in a hybrid in its development does not exceed the best parental form.
Vertically:
So the population of plants artificially created by man?
What is the name of the method at which various crossing of organisms are carried out?
Horizontally:
At the heart of this method, which is still used still lies the concept designed by another chordvin.
So called the population of animals artificially created by man?
So called population of microorganisms artificially created by man?
The domestication began more than 10 thousand years ago. Its centers mainly coincide with the centers of the diversity and origin of cultivated plants. The domestication contributed to a sharp increase in the level of variability in animals. Hybridization and individual selection are basic methods in animal breeding. Mass selection is practically no applied due to a small number of individuals in the offspring. In the selection of animals, 2 types of hybridization are used.
Inbreeding - related hybridization. Crossing between brothers and sisters or between parents and offspring leads to homozygosity and is often accompanied by a weakening of animals, a decrease in their resistance to adverse conditions, a decrease in fertility. Nevertheless, the inbreeding is used to fasten the characteristic economic signs in the breed.
Outbriding - Unreliable hybridization. This crossing is accompanied by strict selection, which allows to enhance and maintain the valuable qualities of the breed. The combination of related and unrelated hybridization is widely used by breeders to eliminate new breeds of animals. An important direction in the selection of animals is the direction of heterosis. Especially widely, the phenomenon of heterosisis is used for example in poultry farming, for example, when obtaining broiler chickens.
Dogs and wolves cross pretty freely. The wolf is a grave animal with special behavior and developed hunting instinct. His jaw is much more powerful than the dog. The behavior of the hybrids of the wolf and the dog is unpredictable. In order to tame an animal, you must need training
Today we will try to hold a "virtual" excursion among some domestic rocks, and at the same time recall the basic methods of animal breeding.
1. Outbrending was obtained for example, dogian
2. Inbreeding obtained:
Tigrolev - This is a mix of male tiger and lion female. They have a tendency to dwarf and usually in size less than their parents. The males are fruitless, while females sometimes can bring offspring.
Ligr - This is a mix of male lion and female tiger. They are the largest of the feline family in the world. The males are fruitless, while females sometimes can bring offspring.
Levopard. - This is the result of the crossing of the male leopard with a female of a lion. The head of the animal is like a lion's head, while the rest of the body resembles a leopard. In terms of the size of the left, larger than ordinary leopards, they love to climb on the trees and splashing in the water.
3. Pomestic animals have a phenomenon of heterosis: with inter-partial or interspecific crossings in the first-generation hybrids there are particularly powerful development and increase in viability. A classic example of manifestation of heteroze is mule - Hybrid mare and donkey. This is a strong, hardy animal that can be used in much more difficult conditions than parental forms.
Test tasks on the topic "Selection"
1. Outbriding is:
1) crossing between unrelated individuals of one species;
2) crossing various types;
3) nearby crossing;
4) There is no correct answer.
2. Hybrids arising from the crossing of various types:
1) differ in infertility;
2) are characterized by increased fertility;
3) give a prolific offspring when crossing with themselves similar;
4) Always female.
3. The center of origin of cultivated plants is areas where:
1) the largest number of varieties of this species was found;
2) the largest density of the growth of this species is detected;
3) This species is first grown by a person;
4) There is no correct answer.
4. Diversity of cat breeds is the result:
1) natural selection 2) artificial selection
3) mutational process 4) modification variability
5. The feature of the selection of animals is:
1) the inapplicability of hybridization methods;
2) insulse to the most powerful reproduction
3) no mutations
6. The main criterion for establishing kinship between species is:
1) external similarity
2) Genetic similarity
3) General Centers of Origin
7. Studying is the initial stage: a) plant selection, animals; b) plant selection; c) hybridization; d) animal breeding.
Allel - One of the states of the same gene. Allocate dominant (A) and recessive alleles.
Allel genes - genes that determine the alternative development of the same feature and located in the intentible areas of homologous chromosomes.
Alternative features - Signs related to the same property, but expressed differently.
Autosomes - chromosomes, the same in male and female organisms
Bivalent - A pair of conjugating homologous chromosomes.
GENE - a nucleic acid section, which is a unit of function and can change by mutating.
GENETICS- Science on the patterns of heredity and variability of organisms.
GENOME - A combination of genes contained in the haploid set of chromosomes.
Heterozygous individuals - individuals with different alleles of the same gene (AA).
AAVR - the genotype of the digerozygous individual; AAAVSSS - Gogotype Trigometerosigital Oracter
Heterochromosomes (or sex chromosomes) - chromosomes, for which male and female organisms differ from each other.
(XX - homogamine; Hu - heterogamy)
Homozygous individuals - individuals with the same alleles of the same gene.
There are two types of homozigot on dominant, when both alleles are dominant (AA) gene alleles and by recession, when both alleles are recessive (AA).
Homologous chromosomes - chromosomes, the same in size and morphology containing the same number of genes responsible for the same signs and properties of the body.
With all the similarity of homologous chromosomes, they are usually genetically unidenticious, since the genes contained in them, causing the same signs, can be represented by different alleles. In one homologous chromosome there may be a dominant allele of gene (a), and in the other - a recessive allele of the same gene (a).
Digibrid crossing - crossing parental individuals differing in two signs
Dominant allele Gena - Allel, whose action suppresses the effect of another recessive allele of the same gene.
Dominant sign - the sign, the development of which in hybrid individuals suppresses the development of another recessive trait.
VARIABILITY
Codec - manifestation of both alleles in the phenotype of heterozygous individuals (AA).
Cross Hopeer- exchange of plots between homologous chromosomes in the process of their
conjugation.
Mono-librid crossing - crossing parental individuals differently on one basis
HEREDITY - The property of organisms to ensure the material and functional continuity between generations.
POLYMERISM - Such interaction of nonallerant genes, in which the development of a sign is due to the interaction of two or more pairs of genes that have a similar impact on the development of this feature.
Recessive allele Gena
Captured inheritance (Morgana law) - genes localized in one chromosome are linked and transmitted mainly together.
Clutch group - Gennes localized in one chromosome (inherited together)
PHENOTYPE- A combination of external and internal signs and properties of the body caused by the interaction of the genotype with certain conditions of the medium.
Chromemid - One of the two nucleotoidal threads formed by doubling the chromosome in the process of cellular division (or subsidiaries of chromosomes)
Chromosomes - self-reproduced organoids cell kernelwhich are carriers of genes that determine the hereditary properties of cells and organisms.
Centrometer- Section of chromosome, holding together 2 of its threads (chromatids)
Epistasis- this is the interaction between non-allele genes, in which the inhibiting action of one gene is
Amitosis - Direct cell division when the interphase core is divided by hauling without the formation of structures characteristic of carookinosis.
Outbriding- crossing individuals not consisting in close relationship. The opposite of the outbreeding is inbreeding.
Blastomeres- Cells resulting from crushing zygotes at the very beginning of the development of the embryo.
VIEW - The historically established set of individuals united by crossing each other, occupying a certain habitat, characterized by the generality of origin and a similar system of devices to environmental conditions.
The species is genetically closed systemSince individuals of different species are not crossed, therefore, the exchange of genetic information does not occur.
Haplodia - see genomic mutations.
Genealogical method - Method based on the preparation and analysis of pedigrees, indicating the manifestation of the signs of interest to the researcher. This method is used in genetic counseling, as well as in the selection of animals. When analyzing the pedigrees, it is possible to establish the nature of the inheritance of the signs, in many cases it is possible to identify the hidden carriage of genes of any hereditary diseases, to establish genotypes of persons marked in the pedigree, and determine the percentage of the probability of birth of a patient "a child in a family having hereditary burden.
Genomic Mutations - Mutations arising from the change in the number of chromosomes in the Caryotype of the individual.
With a multiple haploid change of the number of chromosomes, polyploid or haploid individuals occur. In case of not a multiple haploid change, the number of chromosomes are formed Aneupo-shaped organisms. For example, under the Down syndrome, people are not 46 chromosomes, but 47, the extra chromosome in the 21st pair, that is, not two here, but three chromosomes. In other words, trisomy on the 21st chromosome causes this hereditary disease.
GENOTYPE- The system of interacting genes localized in the chromosomes of the somatic cell core.
Genofund- A complete set of genes characteristic of a certain species that has developed in the process of its evolution.
The term - the gene pool is used not only relative to the species, but also relative to the population.
Under the genofund of the population should be understood as a complete set of genes characteristic of a certain population of organisms.
HERMAPHRODITE- An organism with developed and functioning male and female sexual systems forming men's and female gamets.
Most often, true hermaphroditism is found in flowering plants (all monocotted species of plants - hermaphrodites), less often in animals (hydra, rain worm, etc.).
Heterozis - (hybrid strength) The property of hybrid organisms to exceed parents on productivity, viability and body sizes.
The phenomenon of heterosise is used in the practice of agriculture, applying hybrid plant seeds for sowing, while getting an increase in the crop. For sowing such a culture as corn, almost only hybrid seeds apply.
The chromosome idiogram is a graphic image of a karyotype chromosome located in a certain order of large to smaller or vice versa.
Germ bag - Female Gametofit in coated plants.
ZYGOTE- fertilized egg, giving the beginning of the development of a new organism.
Down Syndrome - The hereditary disease due to the excess chromosome (trisomy in the 21st chromosome) in the amount instead of 46 in patients - 47 chromosomes. For patients, the following deviations are characteristic: the side cut of the eyes, a large thick language, low-planted, deformed and advanced earrings, mental backwardness, low intelligence and others. Frequency of birth children with Down Daunal disease 1: 600.
Deletion- chromosomal mutation resulting from gaps of chromosome and loss of part of hereditary material.
There are intrachromosomic deletions that occur with the double break on the chromosome body and the loss of the cut-out area, and the end shortages (defishesy).
Genov drift - change in gene frequencies in the population due to the action of random factors.
The gene drift (or genetic and automatic processes) is characteristic of small populations of organisms.
The causes of the gene drift may be natural disasters: flooding, forest fire, epizootia, mass spread of pests or human activity (forest cutting, large-scale application of pesticides, etc.). A sharp reduction in the number of individuals in the population in addition to changes in gene frequencies leads to an increase in close-friendly crossings, an increase in homozygotization of individuals and to a decrease in hereditary variability in the population.
Vavilova N. Law and. - (The law of homologous series in hereditary variability) - types and genera are genetically similar, are characterized by similar rows of hereditary variability with such a correctness that, knowing a number of forms within one species, it can be assumed to find parallel forms within other types and genera.
Vavilov N. I. Law contributes to greater purposefulness in the work of breeders and is consistent with the teachings of Ch. Darwin on parallel variability.
For example, the black color of the grain is detected in rye, wheat, barley, corn and other cereals; An extended shape shape - all cereal.
Hardy Weinberg Law -Theless frequencies of genes in the population do not change from generation to generation under the conditions of ideality of the population
The consequence of the Hardy-Weinberg law is to preserve the ratio of homo- and heterozygotes in populations.
The Hardy-Weinberg law is characteristic of large populations and causes genotypic equilibrium in these populations. IN natural conditions The clear manifestation of the Hardy-Weinberg law can be violated as a result of the mutational process and the action of the selection. Therefore, in natural populations, only a tendency to preserve the ratio of alleles of genes and genotypical equilibrium is observed.
VARIABILITY - The property of organisms to acquire new signs that distinguish them from parents and from each other.
Thus, variability determines the instability of preserving the offspringness and properties of parents. Select genotypic and phenotypic variability. Genothypical - variability due to a change in the structure of the genotype.
The genotypic includes mutational and combinative variability (see mutation, variability combinative).
Printed variability - variability of organisms arising from new combinations of alleles of genes in the genotype of individuals of the offspring obtained from the same pair of parents during sexual reproduction.
The combinative variability is due to the recombination of the hereditary material in the meyosis, in the formation of Games. As a result of combinative variability, native brothers and sisters differ from each other by the set of signs and properties, and also differ from their parents.
Variability modification - This variability, at which, under the influence of environmental conditions, changes the phenotype of individuals unchanged in its genotype.
Modification variability demonstrates diversity in the manifestation of identical genotypes in various environments. M. I. Genotypically due, that is, the boundaries of the variability of the sign are genotypically limited (see the reaction rate).
The variability of ontogenetic - consistently occurring cases of individuals in the process of its growth and development. Also the change in the cell in the process of the edefferentiation also includes ontogenetic variability.
Mealing of phenotypic - change in the individual phenotype unchanged in the structure of its genotype. Phenotypic includes ontogenetic and modifying variability (see the variability of ontogenetic and modification).
Inbrid depression is a decrease in the viability and productivity of individuals as a result of inbreeding.
INBREEDING- closely related crossing of individuals.
Under inbreeding, homozygotization occurs for a number of signs.
INVERSION - intrachromosomal mutation resulting from two or more breaks, rotating the chromosome portion by 180 °.
As a result of inversion, a partial change in the procedure for the location of genes in the chromosome occurs.
Individual selection - Selection of individuals rated by offspring in a number of generations.
Thus, with individual selection, the analysis of the genotype of individuals is analyzed. This selection is used in the removal of new breeds of animals, plant varieties.
CLONE - The offspring of one initial individual, obtained by the useless reproduction of it. For example, a currant clone - plants obtained in rooting cuttings taken from the same currant bush.
Kleinfelter Syndrome - a hereditary disease due to the presence in the karyotype of an additional sexual X chromosome. In the karyotype of patients 47 chromosomes
VARIABILITY
(44 autosomes + xxv). The floor is formed by male with the manifestation of genomomascular, that is, a number of secondary sexual signs are formed on the female type - the development of the Milky glands, the deposition of fat in the field of pelvis and the hips, men's primary and secondary sexual signs are underdeveloped. Patients have high heights reduced mental capacity, increased suggestibility, easy to influence others.
Codoming- Manifestation of both alleles in heterozygous individuals (AA).
For example, the fourth blood group in humans with genotype av. Complementary- The interaction of nonallerant genes is called, with the joint action of which a new feature is developing, which is missing from parents.
CONJUGATION - 1) pairwise temporary rapprochement of homologous chromosomes in meyosis (see Bivalent). 2) Form of the sexual process in some organisms, in which a partial exchange of hereditary material occurs (for example, in diatoms of algae, lower mushrooms, infusories, bacteria).
COPULATION- 1) Penetration of the men's gamete in the female, the compound is Games. 2) sexual intercourse in animals having copulate organs.
CRISS - Cross Inheritance (Inheritance Cross-cross) - Inherited inheritance, when the sign of the mother is manifested only in sons, and the sign of the Father is only in daughters.
The CISS-cross inheritance is observed at x-clutch inheritance, when the mother in both X-chromosomes has a recessive allele of the gene, and in the only X chromosome of the father - the dominant allele of the same gene.
Cross Hopeer - Exchange of plots in the process of conjugation by homologous chromosomes.
Mass selection - Selection of individuals along the phenotype without an analysis of the genotype.
Mass selection is used, as a rule, to restore economic and valuable signs of a variety, that is, to ensure the stability of the varietal characteristics of the plants.
Multiple allelism - series of alleles of the same gene.
The hen allele series arises as a result of multiple mutating the same gene.
MEIOSIS- division of cells with the formation of haploid, genetically non-human cells.
In the genetic sense, meyosis is a mechanism for the distribution of hereditary material during sexual reproduction. The genetic essence of meiosis is that the hereditary material is distributed unequally in quality and is twice as follows. The consequence of recombination of the hereditary material in MEIOSE is the unidentification of the generated heams, the unidenticity of individuals of the offspring obtained from the same pair of parents.
Mendel laws:
1. The law of uniformity (dominance).
The hybrids of the first generation from the pair of alternative features is developing only one sign, the second feature is not manifested.
2. The law of splitting.
In the second generation there is a splitting in a certain quantitative ratio of individuals with dominant and recessive features.
For example, for monohybrid crossing, a splitting is characterized in respect of 3: 1, i.e. three parts of individuals with a dominant sign and 1 part with recessive. For the dihybrid splitting formula 9: 3: 3: 1, for triumphant 27: 9: 9: 9: 3: 3: 3: 1, etc.
3. The law of independent combination or independent inheritance.
Pair of alternative features are inherited independently of each other.
So, in the famous Digibrid crossing of peas in F 2 it turns out a splitting in the ratio. 9 parts of yellow round seeds 3 pieces of yellow wrinkled seeds 3 parts of green round seeds 1 part of green wrinkled seeds
If, analyzing these results, trace the splitting separately for each pair of alternative features, we obtain that in color we have a ratio of 12 parts of yellow to 4 parts of green seeds, reducing to 4, we get splitting 3: 1. Also, regardless of the first pair of signs, the ratio of 3: 1 and in the second pair of signs relating to the form of seeds are preserved.
The second and third legal laws thus demonstrate the discreteness of hereditary units - one of the most important properties of heredity.
4. The law "Purity" Games.
Each gamete from the couple of alleles contains only one allele in the "pure" form.
MITOSIS - the main method of dividing the cell with the genetically identical distribution of hereditary material.
In the genetic sense Mitosis is the main mechanism for the distribution of hereditary material under the bunch of organisms reproduction.
Genetic the essence of mitosis As the distribution mechanism consists in the fact that hereditary material is distributed equifically in both quantities and quality. The consequence of this is the formation of genetically identical cells (organisms) and inheritance of signs on the maternal line.
Mutagenic factors (mutagens) - Various factors in nature, the impact of which causes the appearance of mutations.
For example, mutagenic action can have physical factors (radioactive rays), chemical compounds (benzpins and other connections tobacco smoke), as well as the action of viruses.
MUTANT - The body, which, as a result of mutations, arose a change in any one or more features and properties.
MUTATION - the hopping hereditary change in the phenotype due to the change in the structure of the genotype. See Mutations gene, chromosomal, genomic, generative and somatic.
Allel mutations - Gene mutations resulting from changing the structure of the same gene.
Mutations are generative - mutations resulting from changing the hereditary material of the generative cells (Games).
The generative mutations appear, in contrast to the somatic, in the individuals of the offspring of the first generation (in the event that the mutation is dominant) or individuals of the second and subsequent generations in the process of homozigotization with a closely related crossing (if the mutation is recessive).
Mutations are gene - mutations arising from the change in the structure and functions of one or several genes.
In other words, gene mutations arise on the basis of a change in the structure of DNA molecules or RNA when replacing, inserting, losing nucleotides or other molecular processes.
Mutations somatic - mutations arising in the somatic cells of the body as a result of changing their hereditary material. Somatic mutations are manifested in the phenotype of that organism, in the cells of which they arose and are not transmitted by the individuals of the offspring during sexual reproduction. These mutations can be transmitted to offspring only when the reproduction is born.
Spontaneous mutation - Mutation arising from the effects of natural mutagenic factors of the medium, without special, targeted actions of a person.
Spontaneous mutations have an important all-in-biological value as a material for natural selection.
Chromosomal mutations - mutations resulting from restructuring (recombination) of hereditary material inside chromosomes.
Chromosomal restructuring (x. Aberration) occur on the basis of one or more breaks on the body chromosomes. Chromosomal mutations are divided into the following types:
lack - loss of the chromosome site, inversion - rotation of the cutting section of chromosome 180 ° and embedding it to the previous place, duplication - repeated repetition of the same area of \u200b\u200bchromosome, translocation - moving the chromosomal segment inside
The same chromosome in the other when exchanging segments between homologous or non-homologous chromosomes.
Mutagenez- The process of the emergence of hereditary changes (mutations) under the influence of external or internal mutagenic factors.
Reaction rate - This is a genotypically determined body's ability, when changing environmental conditions, vary the severity of the trait within certain limits.
Nucleotide- Monomer molecules nucleic acids (DNA or RNA). Nucleotides from which nucleic acid molecules consist are a residue compound phosphoric acid, sugar (ribose or deoxyribose) and nitrogenous base (adenine, guanin, cytosine, thimine or uracil).
ONTOGENESIS- A combination of consecutive development processes that cause biochemical, physiological and morphological changes of individuals from the moment of origin before the onset of natural death.
FERTILIZATION- The merger of the male and female Games and the union of their nuclei.
PARTHENOGENESIS - Virgin reproduction based on the development of the embryo from a neop-procreted egg.
FLOOR - A set of signs and properties of the body that ensures its participation in reproducing the offspring and the transfer of hereditary information through Games. Employed female and male floor, representatives of them accordingly produce female or men's gametes - egg cells or spermatozoa. Homogate and heterogament floor. In case of homogamitacy, individual chromosomes are presented by pairs of similar to each other chromosomes (for example, XX).
Homoganese individuals in each gumet will contain a X-sex chromosome. It is more likely to be a female floor, and heterogamous - male. When heterogaming the floor in somatic cells of individuals, sex chromosomes are represented by pairs of various chromosomes (for example, XV) or one sexual chromosome (ho). The heterogamous individuals half of the weight will be with a x-chromosome, and half with a y-chromosome (or without sex chromosome).
POLYMERISM - such interaction of genes when the development of a sign is due to the interaction of two or more pairs of genes that have a similar impact on the development of this feature.
In other words, polymeria is the interaction of non-allelegen genes, unambiguously affecting the development of any sign.
There are cumulative (summing) and non-emulative polymeria. With cumulative polymeria, the effect of the gene dose is observed, the greater the dominant alleles, polymer interacting genes in the genotype, the more intense the sign is expressed and vice versa.
With the non-complative polymerium, the dose effect of the gene is not. It is enough for the presence of one dominant allele of any of the polymer interacting genes to ensure that the sign is fully expressed.
Population - A combination of individuals of one species characterized by a habitat and narrower adaptability to specific living conditions. Populations are genetically open systems, since the individuals of different populations belonging to the same form can be cross each other and give a prolific offspring. Populations of self-evaluating individuals and Passmill populations are characterized by various genetic properties. For self-polisher, the property is characteristic - homozyotization. The essence: in each subsequent generation, heterozygotes are reduced twice, and the number of homozygotes increases. For the cross-section (for pamptic populations) is characterized by the genotypic equilibrium property. The essence of this property is expressed in the law of Hardy-Weinberg.
In a pamctic population, the ratio of alleles of any gene remains the same of the generation into generation.
BREED - artificially created by man population of animals, having certain hereditary features. The sign is the result of the interaction of hereditary information with the conditions of the habitat of the body.
Symptoms lucked with floor - Signs that are caused by genes localized in sex chromosomes.
Distinguish X-clutch and y-clutch signs. Each of these groups of signs are characterized by specific features of inheritance. For X-clutch signs, the Crisses are characterized by the Cross-cross inheritance, and for U-clutch - inheritance by the male line (from the father to sons, from sons to the grandchildren of the male and so on).
Reproduction- The property of living organisms to reproduce themselves like, ensuring the continuity and continuity of life.
Reproduction of clarity - breeding organisms of body cells without the formation of specialized cells - Games.
Exist various methods Mascable breeding: division, disputes, kiln, vegetatively.
Gender breeding - This is the reproduction of organisms carried out by means of specialized cells.
There are different methods of sexual reproduction: copulation, conjugation, parthenogenesis (apomixis), ginogenesis, androgenesis.
Recessive allele Gena - Allel, the action of which is suppressed by the action of another dominant allele of the same gene.
Recessive It is called a sign, the development of which in a hybrid individual is suppressed by the development of the dominant sign.
Chromatida - One of the two longitudinal functioning half chromosomes.
SELECTION- Science on the directional transformation of animals, plants and microorganisms.
The purpose of the selection is to develop the theory and methods for creating new breeds of animals, varieties of plants and strains of microorganisms. Selection also belongs to art, as the selection methods create not only material, but also spiritual values. So, for example, the creation of decorative varieties of plants and decorative animals (fish, birds, dogs) is a creative job as the work of artists, musicians, etc.: Has a spiritual, and not material value.
Variety - artificially created by man population of plants, having certain hereditary features.
TRANSCRIPTION - Synthesis of RNA molecules at the respective DNA sections.
TRANSLOCATION- chromosomal mutation arising from the exchange of sections between non-homologous chromosomes. Broadcast - synthesis of polypeptide chains of proteins in the information RNA matrix according to the genetic code.
PHENOTYPE - A combination of external and internal signs and properties of the body caused by the interaction of the genotype with certain conditions of the medium.
Practically phenotype is the result of the interaction of the genotype with the factors of the medium. The term - the phenotype is often used in a simplified meaning when it comes to the manifestation of one character. For example: in the manifestation of a dominant sign - a dominant phenotype, and when a recessive attribute is manifest, a recessive phenotype.
Chromosomal map - Graphic image of chromosome, indicating the distance and order of the location of the gene localized in it.
Chromosomes - self-reproducing cell core organoids that are carriers of genes that determine the hereditary properties of cells and organisms.
Centrometer - The mechanical center of the chromosome, to which the filaments of the separation of division in metaphase and anafase of mitosis and meiosis are attached.
Cytoplasmic inheritance - Inheritance of a sign caused by cytoplasm organodes containing DNA (mitochondria, plasts, centrioli).
For cytoplasmic inheritance, inheritance is characterized by the maternal line, since female gamets contain more cytoplasm, and men's, as a rule, are deprived of it.
STRAIN - artificially created by man population of microorganisms, having certain hereditary features.
Shereshevsky - Turner Syndrome - The hereditary disease caused by the lack of one sex chromosome. Instead of a pair of genital chromosomes in the karyotype of patients with only one x chromosome. The floor is formed female, with characteristic deviations from the norm: underdeveloped primary and secondary female sexual signs, as a rule, such women
sterile (not capable of sexual reproduction), have low growth, short trapezoidal, from the dorsal side, neck, possibly baldness of male type, hair growth on the chest, as well as the growth of mustache and beard.
Epistasis- This is the interaction between the two non-allelese genes, in which the action of one gene is suppressed by another.
Distinguish between dominant and recessive epistasis.
Dominant epistasis - When the dominant allele of one gene suppresses the action of the dominant and recessive allele of the other gene.
Recessive epistasis - when a recessive allele of one gene suppresses the action of the dominant and recessive allele of another gene.
Exercise 1.Fill in the pass in the proposed statements.
1. The artificial population of individuals of one species derived by a person with a certain practical purpose is called ... or ....
2. The collection of world wheat varieties was created ... and stored in ....
3. The most traditional selection methods are ... and ....
4. The most effective form of selection is ... Selection.
5. Forced self-pollization of cross-peer plants is called ....
6. Inbreeding is ... Breeding Pets.
7. The most common type of crossing in the selection of animals is ....
8. Hybrids from crossing genetically different-quality parental forms are characterized by ....
9. Remote hybrids and in plants, and in animals, as a rule, ....
10. Triticale is an allopolypoid wheat hybrid with ....
11. Somatic hybridization is hybridization on ... level.
12. Transgenic is called individuals in the genome of which there are ... Genetic information.
13. Genetically homogeneous offspring, obtained from one individual, is called ....
Control questions
1. What is the purpose of planting plant species as the starting material for selection?
2. What is the introduction?
3. For what signs of the breeder displays new varieties and breeds?
4. Knowledge of what law helps a breeder in finding spontaneous mutations?
5. What was the stimulus for the development of radiation selection?
6. What is the purpose of expulsion of seeds, growth points and other parts of the plants?
7. What types of variability uses a breeder when creating new plants and animals?
8. What is Inzucht?
9. For what purpose are the inbred lines are created?
10. What is heterosis and what is his mechanism?
11. What does an obstacle for remote hybridization?
12. What are the ways to overcome plant underestimation?
13. What is the cause of infertility of remote hybrids?
14. How is the mass selection differs from individual?
15. What is the selective advantage of polyploid plants?
16. What plants are called amphidiploids?
17. What is the mechanism of action of colchicine?
18. For what purpose are the haploid plants?
19. What is indicated by the term "green revolution"?
20. How do transgenic plants get?
21. What is somatic hybridization and for what purpose do it produce?
22. What are animal cloning prospects?
23. Which of the domestic breeders do you know?
When preparing for the Biology Exam, books also use books:
The definition of the concept of "appearance" seems to be very difficult.
We will consider the appearance as a historically established set of organisms that occupy a certain habitat, and characterized by the generality of origin, a similar system of devices to the levels of the medium and reproduction in generations of the main adaptive features and signs.
The organisms of the same species have characteristic of this type of phenotype and genotype other than those in the organisms of another species.
The view occupies a certain area. The distribution area of \u200b\u200bsome species is wide, and such species are usually politicizable - include several geographic races, or subspecies. Other species have a significantly more limited area, they, as a rule, do not form geographic races and are monotypic. The individuals forming the species do not form a constant homogeneous mass. Each body of the species, possessing common and characteristic features, has its own individual genotypic features, which are in the aggregate hereditary variability of the species, or, as sometimes called the "genuofund" of the species.
View, representing a single totality of organisms, is dissected for separate populations. Population They call a combination of freely crossing individuals of one species characterized by the generality of habitat and adaptation to these conditions of existence. The population is under the influence of the condition of existence on the basis of interaction of heredity, variability and selection. The formation of populations is a peculiar way of "fit" of the species to the specific conditions for its existence. The rocks of animal and varieties of plants created by artificial selection are also represented by separate populations.
The processes of formation of populations and their dynamics are microevolution. The emergence of new species begins with the divergence - dismemberment of the type of separate, uncut or isolated groups of organisms. The population is a kind of "forge" in which the natural selection creates new forms.
In the nature of the population of each species is characterized by genetic diversity. But we often do not notice it. The individuals of the population and the species appear to us relatively monotonous. This relative monotony of animals and plants, allowing the systematics to attract animals and plants to certain species, subspecies, races, is created by natural selection. The selection provides not only a variety, but also monotony inside the species.
However, the specified monotony refers only to the main typical features, features and properties of organisms of this population. As soon as we begin to genetically analyze the composition of the population in detail, decomposing it into separate lines, so now we will find huge genotypic variability. In this case, it turns out that each population, within which individuals broke up for a long time with each other, in a limited area in these climatic conditions inherent in the nature of variability.
Sources of hereditary variability in the population are mutational and combinative variability. The effect of genetic laws in the population is subject to the subject of research of genetics of populations.
In nature there are no two organisms, absolutely similar to the genotype. Zoologists or botanists studying biological processes from a group of individuals always deal with a hereditary heterogeneous group of organisms. But since they are studied by a phenotype of organisms, they have the right to neglect the genetic diversity of their material.
The study of the population can be carried out a purely descriptive method. In this case, they determine the phenotypic characteristic of the form of the population, its biological features, find out the conditions of the existence and relationship of organisms, the supply chain, competition, the dynamics of the number by year and its dependence on various factors. The populations are isolated and folded as a result of the action of many factors: the method of reproduction, the nature of variability, changes in the number of individuals, the tempo and direction of selection, climatic, geographical and physiological isolation. The main of them is the selection of signs that ensure the process of reproducing generations, i.e. reproduction. It is obvious that with different ways of reproduction, the emergence and maintenance of populations is carried out by different ways, which one can see, comparing the populations of cross-fertilizing (allogam) and self-evalking (autogamous) organisms.
For the existence of the population are of paramount importance different types hereditary variability: gene mutations, chromosomal restructuring and polyploidy. Interesting changes can only play a limited role. Organisms, genotypically differing, for example, by one gene, morphologically may not differ from each other, but possess various physiological features (viability, duration of development, fertility). Genetic methods make it possible to make a more complete picture of the hereditary potencies of the population, its adaptive features and the direction of evolution.
The prosecutor's studies should be recognized by breeders, for in order to identify the variety of genotypes in populations, it was necessary to isolate, pick up separate pairs of parents and then explore their offspring in a number of generations. This is how breeders came, creating various varieties and rocks. However, the scientific foundations of the genetic study of the population could be laid only after the opening of the city of Mendel, which established the quantitative patterns of inheritance.
The first scientific study of the population, combining genetic and statistical methods, was undertaken by the Danish physiologist of plants and genetics V. Johannsen. His classical work "On inheritance in populations and clean lines", published in 1903, marked the beginning of the genetic study of populations. As often happens in science, the classic discovery is made on the elementary, at first glance, the phenomenon and when using a simple technique. So in this case, V. Johannsen elected the object of study of the population not crosswise, and self-polishing plants - barley, beans and peas. Methodically, it simplified the work, since each such population could be easily decomposed on groups of descendants of individual individuals, i.e., produce separate, "clean", lines. "Clean line," he wrote, "I call individuals that occur from one self-polishing individual." It is clear that the population of absolute self-fillers consists only of pure lines, the individuals of which in nature can be mixed, but cannot be affected by crossing. "
As signs, the weight and size of seeds were taken. These quantitative features are determined by the action of many genes, i.e. are determined by polygenic, and volatility is strongly subject to the influence of the external environment - composition of the soil, climate, method of planting plants, etc. Therefore, to establish the nature of their inheritance, it is necessary to use mathematical methods. Analysis of variability.
According to these features there is a pronounced modification, or pararatipical, variability. The meaning of this variability for evolution in biology there were various points of view. Supporters of the theory of inheritance of acquired properties believed that the changes caused by the impact of the factors of the external environment are inherited, transmitted to the offspring. Opponents of this theory denied the inheritance of modification changes. The solution to this dispute in favor of the latter was fundamental importance, since the selection of organisms along the phenotype without detection of hereditary potencies had a wide distribution in breeding and braked the removal of rocks of animals and plant varieties.
Johannsen conducted a seed weighing one bean variety and built a variational series according to this indicator. Seed weight turned out to be variable in the range from 150 to 750 mg. In the future, seeds weighing from 250 to 350 mg were highlighted separately from seeds weighing 550-650 mg. From each growing plant, seeds were weighted again. Since the beans is self-polished plant, the genotype of seeds from one plant should be the same, and seeds from different plants can be genotypical differences. Therefore, severe seeds (550-650 mg) and light (250-350 mg) selected from a variety representing the population, they gave plants whose seeds were significantly different in weight. The average seed weight on plants grown out of heavy seeds amounted to 518.7 mg, and on plants grown out of light seeds - 443.4 mg. This showed that the bean variety population consists of genetically different plants, each of which can become a twin-palist of a clean line.
For 6-7 generations, Johannsen also selected heavy and light seeds from each plant separately, i.e., it took the selection within cleanlines. With such a selection, it did not have a shift in a number of generations towards heavy or lung seeds. Consequently, the variability in the weight of seeds inside the net line was an unetebled, modification.
As a result of his studies, Johannsen came to the following conclusions: 1) "The selection in the population causes ... A greater or smaller shift - in the direction of the selection - that middle a sign, around which, fluctuating, varies with the relevant individuals" and 2) "Inside the net regression lines (degree The similarities of a sign of offspring with maternal) was ... complete; Selection inside clean lines did not cause any type offset. "
As we see, the population of autogaman plants consists of genotypically heterogeneous lines. Plants of such a population do not cross each other and do not exchange inheritance information. In this case, the existence of a population is based on a strict natural selection of a certain genotype lines, on the generality of adaptive mechanisms to the same type of environmental conditions. In other words, the change in the population of autogaman plants and animals is carried out by the selection of certain hereditary differing lines and clones that have adaptive advantages.
In self-depot rate, a separate organism can be due new race, subspecies and species, as well as varieties or breeds. For example, a new wheat variety can be removed from one grain selected from the population.
However, speaking of high homozygility in clean lines, it should be borne in mind that even clean lines cannot be absolutely homozygous in the following circumstances. First, bond (absolute) self-populated plants do not exist. In self-population populations, such as wheat, tomatoes, etc., always with one or another frequency there are plants with open flowering and cross-pollination. By virtue of this, between clean lines in populations, although rarely, but the processes of crossing and, accordingly, the exchange of hereditary information is performed. Secondly, self-population plants meet mutations that prevent self-pollization (incompatibility). Thirdly, in clean lines of self-population, even in one generation there is a very tangible amount of various mutations that violate the homogeneity of the pure line.
Due to these reasons for the variety of self-population plants during reproduction in production, some of their varieties may lose and require constant control, which is based on the need for quenching.
In the vegetative reproduction of the agonymic organisms that do not have sexual process or the secondaryly lost it (some simplest, mushrooms, algae, etc.), the object of selection in the population is individual clones. Genetic integrity (integration) of such clones in the population is very low due to the impossibility of embodiments between individual clones, but such populations seems to exist in nature and are supported by selection based on symbiotic relations of different genotypes.
In cross-fertilizing organisms in nature, the population is formed on the basis of free crossing of differential individuals with different genotypes, that is, on the basis of pamix. In this case, the hereditary structure of the next generation is reproduced on the basis of a variety of combinations of various heams in fertilization. This implies that the number of individuals of one or another genotype in each generation will be determined by the frequency of occurrence of different weights produced by genotypically different parental organisms. This means that signs and properties are preserved and are distributed in the population based on the patterns of changes in the frequency of gene distribution. The basis of such changes is the regularities of the inheritance, open by G. Mendel and T. Morgan. Knowing this made it possible to bring the rules for the spread of genes in a pamptic population.
Obviously, those organisms whose genotypes are best provide adaptation to the conditions of existence, produce a greater number of the corresponding weights than less adapted. Consequently, the frequency (occurrence) of one or another gene in the population will also be determined by natural selection.
Community of free-solid genotypically different organisms inside the type of some genetics are called Mendelian population. We prefer to call it pampamctic, since its existence is determined not only by the laws of Mendel, but also by the interaction of all evolution factors that ensure freedom to cross the organisms within the population. The diversity of the genotypes of a pamptic population is the result of mutational and combinative variability. The newly emerged mutation to become the property of the population should be preserved and multiplier, i.e., to be in the composition of the genotypes of a number of organisms. Any mutation in the population has its destiny.
Due to the spread of a large number of diverse mutations in the population of the genotypes of organisms is rich in various mutations, which are most often in the heterozygous state. For example, the number of plants, heterozygous for some mutations, can be a rather high percentage in the population. As the concentration of mutations increases in the population, they go into a homozygous state.
The enormous saturation of the population of mutant genes is characteristic not only for cultivated plants and pets, but, as for the first time, S. S. Chetverikov showed, and for natural populations. At the same time, mutations differ in the population, differing as in their genetic nature (gene mutations and chromosomal restructuring) and in its phenotypical manifestation.
To illustrate the dismemberment of the pamptic population under the action of selection, consider the model experience with an artificially created hybrid population, delivered by American geneticists D. Jones and E. Ist. These two researchers crossed two types of tobacco, distinguished along the length of the whisk (short and long). The plants of the first generation were crossed among themselves, and from the second generation two lines A and B with similar variance on this basis were taken.
The length of the Venchik is determined by many genes, and therefore in F 2 it ranged in these lines ranging from 52 to 88 mm, in the future, in the offspring of the lines taken, it was selected for three generations: in the line A - on a short whisk, and in the line in - On a long whisk. In each generation inside both lines, selected forms were crossed: in line A - with a short wedge, and in the line B - with a long wedge. As we see, already in the fifth generation of the line A and in so much differed that there was no extension (transgression) between them, that is, the maximum wreath length in the line A was less than the minimum length in the line B.
Consequently, by selecting and crossing the selected forms, it is possible to create lines with a different expression of a trait than that of the source population: the selection dismested the population to various genotypes. In this experiment, artificial selection was carried out by one basis with deliberately crossing plants. In nature, natural selection is carried out in many terms and either preserves and maintains a population in a holistic condition, or decomposes it according to specific conditions for existence.
The study of population genetics is carried out by different methods, the main of which are cytogenetic, ecological and physiological, mathematical.
The first two methods are used in the analysis of inheritance in the population - to assess the concentration of mutations and frequencies, mutation. The ecological and physiological method is necessary to assess the effect of abiotic and biotic factors in determining the adaptive value of phenotypes relating to genetically different classes of individuals. At the same time, large experimental capabilities opens up modeling of the selection in artificially created synthetic populations with predetermined genetic parameters - the introduction into a population of certain mutations, inversions, translocations, etc.
The mathematical method allows you to give a strict quantitative description of biological processes. The use of electronic computing machines was particularly promising to simulate the dynamics of the genetic structure of the population, taking into account the complex interaction of many factors. The situation described in this case is significantly approaching the reflection of the true, complex and controversial picture of the evolutionary processes occurring in natural populations of plants and animals.
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