establishes parallelism in the inheritance and variability of organisms. Formulated by N. I. Vavilov in 1920. While studying the variability of characters in species and genera of cereals and other families, N. I. Vavilov discovered that: 1. Species and genera that are genetically close to each other are characterized by identical series of hereditary variability with such regularity that knowing a number of forms for one species, one can predict the presence of identical forms in other species and genera. The closer the genera and Linneons are genetically located in the general system, the more complete the identity in the ranks of their variability. 2. Whole families of plants are generally characterized by a certain cycle of variability passing through all the genera that make up the family.” Although the law initially concerned variability in plants, N.I. Vavilov pointed out its applicability to animals. Theoretical the basis of homology of phenotypic series. variability in related taxonomics. groups is the idea of the unity of their origin through diversification under the influence of nature. selection. Since the common ancestors of currently existing species had a specific, specific set of genes, then their descendants must have, with minor exceptions, the same set of genes. Considering that each gene can mutate in different directions (multiple, allelism) and that the mutation process is non-directional, it is natural to assume that the spectrum of changes in identical genes in individuals of close species will be similar. Thus, the law is based on homology. rows (3. r.) lies parallelism of genotypic. variability in individuals with a similar set of genes. Being theoretical. the basis of comparative genetics, the law explains the polymorphism of species and, thus, justifies the integrity of the species, despite the existence within its boundaries of morphologically clearly distinct forms. On the other hand, the law brings clarity to the phenotypic phenomenon. "homogeneity" plural species, edge may be associated with their heterozygosity and the phenomenon of dominance, which is revealed during inbreeding. 3. r., reflecting the general pattern of the mutation process and the formation of organisms, is biol. the basis of methods for purposefully obtaining the necessary inheritances and changes. He indicates to breeders the directions of art, selection, or, as N.I. Vavilov wrote, “what to look for,” and the search methods can be different: from finding the desired forms in nature or identifying them through inbreeding to obtaining these forms using mutagens. Biochemical mechanisms 3. g.r. are widely studied on various objects - from changes in bacterial metabolism to microbiol processes. synthesis to inheritances, human diseases.
Vavilov's law of homological series
An important theoretical generalization of N. I. Vavilov’s research is the doctrine of homological series he developed. According to the law of homological series of hereditary variability formulated by him, not only genetically close species, but also genera of plants form homological series of forms, i.e., there is a certain parallelism in the genetic variability of species and genera. Close species, due to the great similarity of their genotypes (almost the same set of genes), have similar hereditary variability. If all known variations of characters in a well-studied species are placed in a certain order, then almost all the same variations in character variability can be found in other related species. For example, the variability of ear spinality is approximately the same in soft, durum wheat and barley.
Interpretation by N.I. Vavilov. Species and genera that are genetically close are characterized by similar series of hereditary variability, with such regularity that, knowing the series of forms within one species, one can predict the presence of parallel forms in other species and genera. The closer the relationship, the more complete the similarity in the series of variability.
Modern interpretation of the law
Related species, genera, families have homologous genes and gene orders in chromosomes, the similarity of which is the more complete, the closer the taxa being compared are evolutionarily closer. The homology of genes in related species is manifested in the similarity of the series of their hereditary variability (1987).
Meaning of the law
1. The law of homological series of hereditary variability makes it possible to find the necessary characteristics and variants in the almost infinite variety of forms of various species of both cultivated plants and domestic animals, and their wild relatives.
2. It makes it possible to successfully search for new varieties of cultivated plants and breeds of domestic animals with certain required characteristics. This is the enormous practical significance of the law for crop production, livestock breeding and breeding.
3. Its role in the geography of cultivated plants is comparable to the role of D. I. Mendeleev’s Periodic Table of Elements in chemistry. By applying the law of homological series, it is possible to establish the center of origin of plants according to related species with similar characteristics and forms, which probably develop in the same geographical and ecological environment.
Ticket 4
Inheritance of characteristics during divergence of sex chromosomes (primary and secondary nondisjunction of X chromosomes in Drosophila)
As noted earlier, when a white-eyed female Drosophila is crossed with a red-eyed male F1 all the daughters have red eyes, and all the sons who receive their only X-chromosome from mother, eyes white. However, sometimes in such crossings single red-eyed males and white-eyed females appear, the so-called exceptional flies with a frequency of 0.1-0.001%. Bridges suggested that the appearance of such “exceptional individuals” is explained by the fact that in their mother, during meiosis, both X chromosomes ended up in one egg, i.e. non-divergence occurred X-chromosomes. Each of these eggs can be fertilized either by sperm or X-chromosome, or Y-chromosome. As a result, 4 types of zygotes can be formed: 1) with three X-chromosomes – XXX; 2) with two mothers X-chromosomes and Y-chromosome XXY; 3) with one paternal X-chromosome; 4) without X-chromosomes, but with Y-chromosome.
XXY are normal fertile females. XO- males, but sterile. This shows that in Drosophila Y-chromosome does not contain sex-determining genes. When crossing XXY females with normal red-eyed males ( XY) Bridges found among the offspring 4% white-eyed females and 4% red-eyed males. The rest of the offspring consisted of red-eyed females and white-eyed males. The author explained the appearance of such exceptional individuals by secondary nondivergence X-chromosomes in meiosis, because the females taken in the cross ( XXY), arose as a result of primary chromosome nondisjunction. Secondary chromosome nondisjunction in such females in meiosis is observed 100 times more often than primary.
In a number of other organisms, including humans, nondisjunction of sex chromosomes is also known. Of the 4 types of offspring resulting from nondivergence X-chromosomes in women, individuals who do not have any X-chromosomes die during embryonic development. Zygotes XXX develop in women who are more likely to have mental defects and infertility than usual. From zygotes XXY defective men develop - Klinefelter syndrome - infertility, mental retardation, eunuchoid physique. Descendants from one X-chromosomes often die in embryonic development; the rare survivors are women with Shereshevsky-Turner syndrome. They are short, childish, and sterile. In humans Y-chromosomes contain genes that determine the development of a male organism. With absence Y-Chromosomes develop according to the female type. Nondisjunction of sex chromosomes occurs more frequently in humans than in Drosophila; On average, for every 600 boys born, there is one with Klinefelter syndrome.
LAW OF HOMOLOGICAL SERIES
THE LAW OF HOMOLOGICAL SERIES discovered by N.I. Vavilov (1920) is a law according to which the variability of plant genera and species of close origin occurs in a common (parallel) way. Genetically close genera and species are characterized by similar series of hereditary variability with such regularity that knowing the series of forms within one species, one can predict the presence of parallel forms in other related species and genera. The law of homological series, like D.I. Mendeleev’s periodic system of elements in chemistry, allows, based on knowledge of the general patterns of variability, to predict the existence in nature of previously unknown forms with traits valuable for breeding. Many such forms were found after N.I. Vavilov published the law of homological series. One of the clear examples of the prospects of searching for such forms and the practical application of the law of homological series is the creation of single-seeded varieties of sugar beet. Later studies confirmed the law of homological series in microorganisms and animals, in which parallelism in the variability of morphological and biochemical characters was discovered.
Ecological encyclopedic dictionary. - Chisinau: Main editorial office of the Moldavian Soviet Encyclopedia. I.I. Dedu. 1989.
See what the “LAW OF HOMOLOGICAL SERIES” is in other dictionaries:
law of homological series- homologinių eilių dėsnis statusas T sritis augalininkystė apibrėžtis Lygiagretaus organizmų kitimo dėsnis, pagal kurį genetiškai artimoms augalų rūšims, gentims ir šeimoms yra būdingos lygiagretės (homologinė s) paveldimųjų požymių ir savybių… … Žemės ūkio augalų selekcijos ir sėklininkystės terminų žodynas
law of homological series- biol. A pattern establishing parallelism in the variability of related groups of plants (discovered by Academician N. I. Vavilov) ... Dictionary of many expressions
Homologous series in hereditary variability is a concept introduced by N.I. Vavilov when studying parallelisms in the phenomena of hereditary variability by analogy with homologous series of organic compounds. Patterns in... ... Wikipedia
See Homologous series in the law of hereditary variability. .(Source: “Biology. Modern illustrated encyclopedia.” Editor-in-chief A. P. Gorkin; M.: Rosman, 2006.) ...
Variability, a law developed by the Soviet scientist N.I. Vavilov that establishes parallelism in the variability of organisms. Even Charles Darwin (1859 68) drew attention to the far-reaching parallelism in the variability (See Variability) of close... ... Great Soviet Encyclopedia
Establishes parallelism in the inheritance and variability of organisms. Formulated by N. I. Vavilov in 1920. While studying the variability of characters in species and genera of cereals and other families, N. I. Vavilov discovered that: 1. Species and genera that are genetically close between ... ... Biological encyclopedic dictionary
Hereditary variability was formulated by N.I. Vavilov in 1920, establishing parallelism in the variability of related groups of plants. As was shown later, this phenomenon is based on gene homology (their identical molecular structure) and... Big Encyclopedic Dictionary
In hereditary variability, formulated by N.I. Vavilov in 1920, it establishes parallelism in the variability of related groups of plants. As was shown later, this phenomenon is based on gene homology (their identical molecular structure)... ... encyclopedic Dictionary
Open Russian geneticist N.I. Vavilov in 1920, a pattern establishing parallelism (similarity) in hereditary (genotypic) variability in related organisms. In Vavilov’s formulation, the law reads: “Species and genera, genetically... ... Biological encyclopedic dictionary
Books
- The law of homological series in hereditary variability, N. I. Vavilov. The book publishes for the first time all three editions of “The Law of Homologous Series in Hereditary Variation,” including the English one from 1922. Also included are works that were published only once…
The law, which was discovered by the outstanding domestic scientist N.I. Vavilov, is a powerful stimulator for the selection of new species of plants and animals that are beneficial to humans. Even now, this pattern plays a big role in the study of evolutionary processes and the development of an acclimatization base. The results of Vavilov’s research are also important for the interpretation of various biogeographical phenomena.
The essence of the law
Briefly, the law of homological series is as follows: the spectra of variability in related types of plants are similar to each other (often this is a strictly fixed number of certain variations). Vavilov presented his ideas at the III selection congress, which took place in 1920 in Saratov. To demonstrate the effect of the law of homological series, he collected the entire set of hereditary characteristics of cultivated plants, arranged them in one table and compared the varieties and subspecies known at that time.
Study of plants
Along with cereals, Vavilov also considered legumes. In many cases parallelism was found. Despite the fact that each family had different phenotypic characteristics, they had their own characteristics and form of expression. For example, the color of the seeds of almost any cultivated plant varied from the lightest to black. Up to several hundred traits have been found in cultivated plants that have been well studied by researchers. In others, which were less studied at that time or wild relatives of cultivated plants, much fewer signs were observed.
Geographical centers of species distribution
The basis for the discovery of the law of homological series was the material that Vavilov collected during his expedition to the countries of Africa, Asia, Europe and America. The first assumption that there are certain geographical centers from which biological species originate was made by the Swiss scientist A. Decandolle. According to his ideas, these species once covered large territories, sometimes entire continents. However, it was Vavilov who was the researcher who was able to study the diversity of plants on a scientific basis. He used a method called differentiated. The entire collection that was collected by the researcher during the expeditions was subjected to careful analysis using morphological and genetic methods. In this way it was possible to determine the final area of concentration of the diversity of forms and characteristics.
Plant map
During these trips, the scientist did not get confused in the variety of species of different plants. He put all the information on maps using colored pencils, then transferring the material into a schematic form. Thus, he was able to discover that there are only a few centers of cultivated plant diversity on the entire planet. The scientist showed directly with the help of maps how species “spread” from these centers to other geographical regions. Some of them go a short distance. Others conquer the whole world, as happened with wheat and peas.
Consequences
According to the law of homological variability, all plant varieties that are genetically close to each other have approximately equal series of hereditary variability. At the same time, the scientist admitted that even outwardly similar characteristics may have a different hereditary basis. Taking into account the fact that each of the genes has the ability to mutate in different directions and that this process can occur without a specific direction, Vavilov made the assumption that the number of gene mutations in related species would be approximately the same. N. I. Vavilov’s law of homological series reflects the general patterns of gene mutation processes, as well as the formation of various organisms. It is the main basis for the study of biological species.
Vavilov also showed a corollary that followed from the law of homological series. It goes like this: Hereditary variability varies in parallel in almost all plant species. The closer the species are to each other, the more pronounced this homology of characters is. Now this law is widely applied in the selection of crops and animals. The discovery of the law of homological series is one of the scientist’s greatest achievements, which brought him worldwide fame.
Origin of plants
The scientist created a theory about the origin of cultivated plants in points of the globe distant from each other in various prehistoric eras. According to Vavilov’s law of homological series, similar variations in the variability of characters are found in related species of plants and animals. The role of this law in crop and livestock production can be compared with the role played by D. Mendeleev’s table of periodic elements in chemistry. Using his discovery, Vavilov came to the conclusion about which territories are the primary sources of certain types of plants.
- The world owes the origin of rice, millet, naked forms of oats, and many types of apple trees to the Sino-Japanese region. Also, the territories of this region are home to valuable varieties of plums and oriental persimmons.
- coconut palm and sugar cane - Indonesia-Indochina Center.
- Using the law of homological series of variability, Vavilov managed to prove the enormous importance of the Hindustan Peninsula in the development of crop production. These territories are home to certain types of beans, eggplants, and cucumbers.
- Walnuts, almonds, and pistachios were traditionally grown in the Central Asian region. Vavilov discovered that this particular territory is the birthplace of onions, as well as the primary types of carrots. Apricots were grown in ancient times. Some of the best in the world are melons that were bred in Central Asia.
- Grapes first appeared in the Mediterranean territories. The process of evolution of wheat, flax, and various varieties of oats also took place here. Also quite typical of the Mediterranean flora is the olive tree. The cultivation of lupine, clover and flax also began here.
- The flora of the Australian continent gave the world eucalyptus, acacia, and cotton.
- The African region is the birthplace of all types of watermelons.
- In the European-Siberian territories, the cultivation of sugar beets, Siberian apple trees, and forest grapes took place.
- South America is the birthplace of cotton. The Andean territory is also home to some types of tomatoes. In the territories of Ancient Mexico, corn and some types of beans grew. Tobacco also originated here.
- In the territories of Africa, ancient man first used only local plant species. The Black Continent is the birthplace of coffee. Wheat appeared for the first time in Ethiopia.
Using the law of homological series of variability, a scientist can identify the center of origin of plants based on characteristics that are similar to the forms of species from another geographical area. In addition to the necessary diversity of flora, in order for a large center of diverse cultivated plants to arise, an agricultural civilization is also needed. This is what N.I. Vavilov thought.
Animal domestication
Thanks to the discovery of the law of homological series of hereditary variability, it became possible to discover those places where animals were first domesticated. It is believed that it happened in three ways. This is the bringing together of humans and animals; forced domestication of young individuals; domestication of adults. The territories where wild animals were domesticated are presumably located in the habitats of their wild relatives.
Taming in different eras
It is believed that the dog was domesticated during the Mesolithic era. People began breeding pigs and goats in the Neolithic era, and a little later wild horses were tamed. However, the question of who the ancestors of modern domestic animals were is not yet clear enough. It is believed that the ancestors of cattle were aurochs, horses - tarpans and Przewalski's horses, and the domestic goose - the wild gray goose. Now the process of domestication of animals cannot be called complete. For example, arctic foxes and wild foxes are in the process of domestication.
The meaning of the law of homological series
With the help of this law, it is possible not only to establish the origin of certain plant species and the centers of domestication of animals. It allows you to predict the occurrence of mutations by comparing mutation patterns in other types. Also, using this law, it is possible to predict the variability of a trait, the possibility of the appearance of new mutations by analogy with those genetic deviations that were found in other species related to a given plant.
Among the flora of the globe, there is a significant number (more than 2500) species of a group of plants cultivated by humans and called cultural. Cultivated plants and the agrophytocenoses formed by them replaced meadow and forest communities. They are the result of human agricultural activity, which began 7-10 thousand years ago. Wild plants that become cultivated inevitably reflect a new stage in their life. The branch of biogeography that studies the distribution of cultivated plants, their adaptation to soil-climatic conditions in various regions of the globe and includes elements of agricultural economics is called geography of cultivated plants.
According to their origin, cultivated plants are divided into three groups:
- the youngest group
- weed species,
- the most ancient group.
Youngest group cultivated plants come from species that still live in the wild. These include fruit and berry crops (apple, pear, plum, cherry), all melons, and some root crops (beets, rutabaga, radishes, turnips).
Weed species plants became objects of culture where the main crop produced low yields due to unfavorable natural conditions. Thus, with the advancement of agriculture to the north, winter rye replaced wheat; The oilseed crop camelina, widespread in Western Siberia and used to produce vegetable oil, is a weed in flax crops.
For most ancient cultivated plants cannot be established when their cultivation began, since their wild ancestors have not been preserved. These include sorghum, millet, peas, beans, beans, and lentils.
The need for source material for breeding and improving varieties of cultivated plants led to the creation of the doctrine of their centers of origin. The teaching was based on Charles Darwin’s idea of the existence geographical centers of origin of biological species. The geographical areas of origin of the most important cultivated plants were first described in 1880 by the Swiss botanist A. Decandolle. According to his ideas, they covered quite vast territories, including entire continents. The most important research in this direction, half a century later, was carried out by the remarkable Russian geneticist and botanist-geographer N.I. Vavilov, who studied the centers of origin of cultivated plants on a scientific basis.
N.I. Vavilov proposed a new one, which he called differentiated, a method for establishing the original center of origin of cultivated plants, which is as follows. A collection of the plant of interest collected from all places of cultivation is studied using morphological, physiological and genetic methods. Thus, the area of concentration of the maximum diversity of forms, characteristics and varieties of a given species is determined.
The doctrine of homological series. An important theoretical generalization of N. I. Vavilov’s research is the doctrine of homological series he developed. According to the law of homological series of hereditary variability formulated by him, not only genetically close species, but also genera of plants form homological series of forms, i.e., there is a certain parallelism in the genetic variability of species and genera. Close species, due to the great similarity of their genotypes (almost the same set of genes), have similar hereditary variability. If all known variations of characters in a well-studied species are placed in a certain order, then almost all the same variations in character variability can be found in other related species. For example, the variability of ear spinality is approximately the same in soft, durum wheat and barley.
Interpretation by N. I. Vavilov. Species and genera that are genetically close are characterized by similar series of hereditary variability, with such regularity that, knowing the series of forms within one species, one can predict the presence of parallel forms in other species and genera. The closer the relationship, the more complete the similarity in the series of variability.
Modern interpretation of the law. Related species, genera, families have homologous genes and gene orders in chromosomes, the similarity of which is the more complete, the closer the taxa being compared are evolutionarily closer. The homology of genes in related species is manifested in the similarity of the series of their hereditary variability (1987).
The meaning of the law.
- The law of homological series of hereditary variability makes it possible to find the necessary characteristics and variants in the almost infinite variety of forms of various species of both cultivated plants and domestic animals, and their wild relatives.
- It makes it possible to successfully search for new varieties of cultivated plants and breeds of domestic animals with certain required characteristics. This is the enormous practical significance of the law for crop production, livestock breeding and breeding.
- Its role in the geography of cultivated plants is comparable to the role of D. I. Mendeleev’s Periodic Table of Elements in chemistry. By applying the law of homological series, it is possible to establish the center of origin of plants according to related species with similar characteristics and forms, which probably develop in the same geographical and ecological environment.
Geographical centers of origin of cultivated plants. For the emergence of a large center of origin of cultivated plants, N.I. Vavilov considered a necessary condition, in addition to the richness of wild flora in species suitable for cultivation, the presence of an ancient agricultural civilization. The scientist came to the conclusion that the vast majority of cultivated plants are connected by 7 main geographical centers of their origin:
- South Asian tropical,
- East Asian,
- South-West Asian,
- Mediterranean,
- Ethiopian,
- Central American,
- Andean.
Outside these centers there was a significant territory that required further study in order to identify new centers of domestication of the most valuable representatives of wild flora. The followers of N.I. Vavilov - A.I. Kuptsov and A.M. Zhukovsky continued research into the study of the centers of cultivated plants. Ultimately, the number of centers and the territory they covered increased significantly, there were 12 of them
- Sino-Japanese.
- Indonesian-Indochine.
- Australian.
- Hindustan.
- Central Asian.
- Near Asian.
- Mediterranean.
- African.
- European-Siberian.
- Central American.
- South American.
- North American