On June 4, he made a presentation "The law of homological series in hereditary variability." This is one of those works that are considered fundamental and are the theoretical basis biological research. The essence of the law is that species and genera that are genetically close ( bound friend with another unity of origin), are characterized by similar series in hereditary variability. Student enthusiasm for the study of cereals, and then cruciferous, legumes, pumpkins, allowed Vavilov and his students to find mutations that are similar in related species, and then genera. In the table developed as a result of the experiments, Vavilov noted the mutations, the manifestation of which was found in these species, with a “+” sign, and empty spaces indicate that such mutations should be, but have not yet been discovered. A table with empty cells that will be filled in with the further development of science. Where have we met with something like this? Of course, in chemistry, the famous periodic table! The regularity of the two laws is confirmed by science. "Empty" cells are filled, and this is the basis for practical selection. Durum wheat is known only in the spring form, but on the basis of the law, durum wheat in the winter form should also exist in nature. Indeed, it was soon discovered on the border of Iran and Turkey. Pumpkins and melons are characterized by simple and segmented fruits, but watermelon of this form was not described at the time of Vavilov. But segmented watermelons have been found in the southeast of the European part of Russia. The culture is dominated by the cultivation of three-sprout beets, the crops of which require weeding and removal of two extra shoots. But among the relatives of beets in nature there were also single-sprouted forms, so scientists were able to create a new variety of single-sprouted beets. awnless cereal crops- a mutation that proved useful in the introduction of machine harvesting, when the mechanisms become less clogged. Breeders, using the Vavilov law, found awnless forms and created new varieties of awnless cereals. The facts of parallel variability in close and distant species were already known to C. Darwin. For example, the same coat color of rodents, albinism in representatives different groups fauna and humans (a case of albinism in Negroes is described), lack of plumage in birds, lack of scales in fish, similar coloring of fruits of fruit and berry crops, variability of root crops, etc. The reason for the parallelism in variability lies in the fact that the basis of homologous characters lies the presence of similar genes: the genetically closer the species and genera, the more complete the similarity in the series of variability. Hence - the cause of homologous mutations - the common origin of genotypes. Live nature in the process of evolution it was programmed, as it were, according to one formula, regardless of the time of origin of the species. The law of homological series in hereditary variability by NI Vavilov was not only a confirmation of Darwin's theory of the origin of species, but also expanded the idea of ​​hereditary variability. Nikolai Ivanovich can again be proclaimed: “Thanks to Darwin!”, but also “Continuing Darwin!” Let's go back to 1920. The recollections of eyewitnesses are interesting. Alexandra Ivanovna Mordvinkina, who was present at the congress of the Saratov Agricultural Institute (later a candidate of biological sciences), recalled: “The congress opened in the largest auditorium of the university. Not a single report subsequently made such a strong impression on me as the speech of Nikolai Ivanovich. He spoke with inspiration, everyone listened with bated breath, it was felt that something very big and new in science was opening before us. When there was a stormy, long-lasting applause, Professor Vyacheslav Rafailovich Zelensky said: "These are biologists who greet their Mendeleev." The words of Nikolai Maksimovich Tulaikov especially imprinted in my memory: “What can be added to this report? I can say one thing: Russia will not perish if it has such sons as Nikolai Ivanovich. Nikolai Vladimirovich Timofeev-Resovsky, an excellent geneticist who knew Vavilov not only by work, but also personally, spoke confidentially to close acquaintances: “Nikolai Ivanovich was a wonderful person and great martyr, an excellent plant grower and gatherer, a traveler, a brave and universal favorite, but his law of homology series - the law is not at all homological, but analogous series, yes, sir! What is homology? This similarity is based on common origin. What is an analogy? similarity external signs, which is determined by similar habitat, but not kinship. So who is right? Vavilov! One can only admire the depth of his biological mind! Changing just one term in the title also changes the essence of the law. According to the law of homological series, all people are equal, because they are of the same biological origin, and belong to the homo sapiens species, i.e. everyone is equally smart, capable and talented, etc., but they have external differences: in height, proportions between body parts etc. According to the law of analogous series, people are outwardly similar, because they have a similar habitat, but different origin. And this is already room for chauvinism, racism, nationalism, up to genocide. And the Vavilov law says that the pygmy of Africa and the basketball player of America are of the same genetic root, and one cannot be placed over the other - this is unscientific! The validity of the universal biological regularity discovered by Vavilov has been confirmed by modern research not only in plants, but also in animals. Modern geneticists believe that the law reveals boundless prospects scientific knowledge, generalizations and foresight” (Professor M. E. Lobanov). Another one belongs to the Saratov period. fundamental work N. I. Vavilova - “Plant immunity to infectious diseases"(1919). On title page Book Nikolai Ivanovich wrote: "Dedicated to the memory of the great researcher of immunity Ilya Ilyich Mechnikov." No great scientist sees himself as a stand-alone in science. So Vavilov, thanks to Mechnikov, asked himself the question, can plants have protective forces if animals have them? In search of an answer to the question, he conducted research on cereals original methodology and, summarizing practice and theory, laid the foundations of a new science - phytoimmunology. The work was of purely practical importance - to use the natural immunity of plants as the most rational and cost-effective way to control pests. The young scientist created an original theory of the physiological immunity of plants to infectious diseases, and the study of genotypic immunity formed the basis of the doctrine. N. I. Vavilov studied the reaction of the "host" to the introduction of the parasite, the specificity of this reaction, and found out whether the entire series is immune, or only certain types of this series. Special meaning Nikolai Ivanovich gave group immunity, believing that in breeding it is important to breed varieties that are resistant not to one race, but to whole population physiological races, and it is necessary to look for such resistant species in the homeland of the plant. Science later confirmed that wild species- relatives of cultivated plants - have natural immunity and are less susceptible to infectious diseases. It is the introduction of resistance genes into plants that modern breeders are engaged in, using the theory of N. I. Vavilov and methods genetic engineering. The scientist was interested in the development of immunity issues throughout his entire career. scientific activity: “The doctrine of plant immunity to infectious diseases” (1935), “The laws of natural plant immunity to infectious diseases (keys to finding immune forms)” (published only in 1961). Academician Petr Mikhailovich Zhukovsky rightly noted: “In the Saratov period, although it was short (1917-1921), the star of N. I. Vavilov, the scientist, rose.” Later, Vavilov would write: “I migrated from Saratov in March 1921 with the entire laboratory of 27 people.” He was elected head of the Bureau of Applied Botany of the Agricultural Scientific Committee in Petrograd. From 1921 to 1929 - Professor of the Department of Genetics and Breeding of the Leningrad Agricultural Institute. In 1921, V. I. Lenin sent two scientists to a conference in America, one of them - N. I. Vavilov. The report on genetic research made him popular among the scientists of the conference. In America, his performances were accompanied by a standing ovation, similar to the one that was later for Chkalov. “If all Russians are like that, then we need to be friends with them,” American newspapers shouted. In the 20-30s. N. I. Vavilov also manifests himself as a major organizer of science. He was actually the founder and permanent leader of the All-Union Institute of Plant Industry (VIR). In 1929, the All-Union Academy of Agricultural Sciences (VASKhNIL) was created on the basis of the All-Union Institute of Experimental Agronomy, which had previously been organized by Vavilov. He was elected the first president (from 1929 to 1935). With the direct participation of the scientist, the Institute of Genetics of the USSR Academy of Sciences was organized. Behind short term Vavilov's talent created a scientific school of geneticists, which became the world's leading one. All the initial work in our country in the field of genetics was carried out by him or under his direction. In VIR, the method of experimental polyploidy was first used, and G. D. Karpechenko began work on its use in distant hybridization. Vavilov insisted on starting work on the use of the phenomenon of heterosis and interline hybridization. Today it is the ABC of selection, but then it was the beginning. Over 30 years of scientific activity, about 400 works and articles have been published! Phenomenal memory, encyclopedic knowledge, knowledge of almost twenty languages, aware of all the innovations in science. He worked 18-20 hours a day. Mom scolded him: “You don’t even have time to sleep ...,” recalls Vavilov’s son.

Among the flora the globe a significant number (more than 2500) species group of plants cultivated by man and called cultural. Cultivated plants and agrophytocenoses formed by them have replaced meadow and forest communities. They are the result of human agricultural activity, which began 7-10 thousand years ago. Wild plants passing into cultivation inevitably reflect a new stage in their life. The branch of biogeography that studies the distribution of cultivated plants, their adaptation to soil and climatic conditions in various areas the globe and including elements of the agricultural economy 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.

The youngest group cultivated plants comes from species that still live in the wild. These include fruit and berry crops (apple, pear, plum, cherry), all gourds, some root crops (beets, rutabaga, radishes, turnips).

Weed species plants have become objects of culture where the main culture due to unfavorable natural conditions gave low yields. So, with the advancement of agriculture to the north, winter rye replaced wheat; widely distributed in Western Siberia, the oilseed camelina, used to obtain vegetable oil, is a weed in flax crops.

For most ancient cultivated plants, it is impossible to establish the time of the beginning of their cultivation, since their wild ancestors have not been preserved. These include sorghum, millet, peas, beans, beans, 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 doctrine was based on the idea of ​​Charles Darwin about the existence geographical centers of origin of biological species. For the first time, the geographical areas of origin of the most important cultivated plants were described in 1880 by the Swiss botanist A. Decandol. 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, named by him differentiated the method of establishing the initial center of origin of cultivated plants, which is as follows. Collected from all places of cultivation, the collection of the plant of interest is examined using morphological, physiological and genetic methods. Thus, the area of ​​concentration of the maximum diversity of forms, features and varieties of a given species is determined.

The doctrine of homological series. An important theoretical generalization of N. I. Vavilov’s research is his theory of homological series. 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 the known variations of characters in a well-studied species are arranged in a certain order, then in other related species one can find almost all the same variations in the variability of characters. For example, the variability of the ear awn is approximately the same in soft, durum wheat and barley.

Interpretation by N. I. Vavilov. Species and genera genetically close are characterized by similar series of hereditary variability, with such regularity that, knowing the number of forms within one species, one can foresee the finding 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 evolutionarily closer compared taxa. 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.

  1. The law of homologous series of hereditary variability makes it possible to find necessary signs and variants in an almost infinite variety of forms various kinds 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 traits. This is the enormous practical significance of the law for crop production, animal husbandry and selection.
  3. Its role in the geography of cultivated plants is comparable to that of Periodic system elements of D. I. Mendeleev in chemistry. Applying the law of homologous series, it is possible to establish the center of origin of plants by related species with similar features and forms, which probably develop in the same geographical and ecological setting.

Geographic centers of origin of cultivated plants. For the emergence of a large center of origin of cultivated plants, N. I. Vavilov considered necessary condition, in addition to the wealth of wild flora 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 associated with 7 main geographical centers of their origin:

  1. South Asian tropical
  2. East Asian,
  3. southwest asian,
  4. mediterranean,
  5. Ethiopian
  6. Central American,
  7. Andean.

Outside these centers, there was a significant territory that required further study in order to identify new centers of cultivation of the most valuable representatives wild flora. The followers of N. I. Vavilov - A. I. Kuptsov and A. M. Zhukovsky continued their research on the study of the centers of cultivated plants. Ultimately, the number of centers and the area covered by them increased significantly, there were 12 of them

  1. Sino-Japanese.
  2. Indonesian-Indochinese.
  3. Australian.
  4. Hindustani.
  5. Central Asian.
  6. Anterior Asian.
  7. Mediterranean.
  8. African.
  9. European-Siberian.
  10. Central American.
  11. South American.
  12. North American

homologous series). Formulated in 1920 by N. I. Vavilov, who discovered that the hereditary variability of plants is similar in closely related species and genera of the grass family. It manifests itself in a change in similar characters with such regularity that, knowing the forms of plants in representatives of one species, one can foresee the appearance of these forms in other related species and genera. How closer friend the species stand next to each other by origin, the more clearly this similarity is manifested. So, in different types of wheat (for example, soft and durum), rows of similar hereditary changes are revealed in the awn of the ear (awned, semi-awned, awnless), its color (white, red, black, gray ears), the shape and texture of the grain, early maturity, cold resistance , responsiveness to fertilizers and so on.

Similar variability in the awning of the ear in soft wheat (1-4), durum wheat (5-8) and six-row barley (9-12) (according to N. I. Vavilov).

The parallelism of variability is more weakly expressed in different genera within a family (for example, wheat, barley, rye, oats, couch grass and other genera from the family of cereals) and even weaker in different families within an order (higher taxonomic rank). In other words, in accordance with the law of homology series, closely related species due to the great similarity of their genomes (almost identical sets of genes) have similar potential variability of traits, which is based on similar mutations of homologous (orthologous) genes.

N. I. Vavilov pointed out the applicability of homological series of laws to animals as well. Obviously, this is a universal law of variability, covering all the kingdoms of living organisms. The validity of this law is vividly illustrated by genomics, which reveals the similarity of the primary structure of the DNA of closely related species. The law of homology series finds further development in the modular (block) principle of the theory of molecular evolution, according to which the genetic material diverges through duplications and subsequent combinatorics of DNA sections (modules).

The law of homology series helps to purposefully search for hereditary changes necessary for selection. It indicates to breeders the direction of artificial selection, facilitates the production of forms that are promising for the selection of plants, animals and microorganisms. For example, guided by the law of homology series, scientists have created alkaloid-free (non-bitter) varieties of fodder lupins for pasture animals, while enriching the soil with nitrogen. The law of homology series also helps to navigate in the choice of model objects and specific genetic systems (genes and traits) for modeling and searching for therapy. hereditary diseases human, such as metabolic diseases, neurodegenerative, etc.

Lit .: Vavilov N. I. The law of homological series in hereditary variability. M., 1987.

S. G. Inge-Vechtomov.

Processing of extensive material of observations and experiments, detailed study of the variability of numerous Linnean species (Linneons), great amount new facts, obtained mainly in the study of cultivated plants and their wild relatives, allowed N.I. Vavilov to bring everything into a single whole notable examples parallel variability and formulate common law, called by him "The law of homological series in hereditary variability" (1920), reported by him at the Third All-Russian Congress of Breeders, held in Saratov. In 1921 N.I. Vavilov was sent to America for International congress By agriculture, where he made a presentation on the law of homologous series. The law of parallel variability of closely related genera and species, established by N.I. Vavilov and associated with a common origin, developing the evolutionary teachings of Charles Darwin, was duly appreciated by world science. It was perceived by the audience as the biggest event in the world biological science, which opens the widest horizons for practice.

The law of homological series, first of all, establishes the foundations of the taxonomy of a huge variety of plant forms, which are so rich in organic world, allows the breeder to get a clear idea of ​​the place of each, even the smallest, systematic unit in the plant world and to judge the possible diversity of the source material for selection.

The main provisions of the law of homological series are as follows.

"1. Species and genera that are genetically close are characterized by similar series of hereditary variability with such regularity that, knowing the number of forms within one species, one can foresee the occurrence of parallel forms in other species and genera. The closer genetically located in common system genera and linneons, the more complete is the similarity in the series of their variability.

2. Whole families of plants are generally characterized by a certain cycle of variability passing through all the genera and species that make up the family.

Even at the III All-Russian Congress on Selection (Saratov, June 1920), where N.I. Vavilov reported his discovery for the first time, all participants of the congress recognized that “like the periodic table (periodic table)” the law of homological series will allow predicting the existence, properties and structure of still unknown forms and species of plants and animals, and highly appreciated the scientific and practical significance of this law . Modern advances in molecular cell biology make it possible to understand the mechanism of existence homological variability in close organisms - what exactly is the basis for the similarity of future forms and species with existing ones - and meaningfully synthesize new forms of plants that are not found in nature. Now new content is being introduced into Vavilov's law, just like the appearance quantum theory gave a new deeper content to Mendeleev's periodic system.

Vavilov's law of homological series

An important theoretical generalization of N. I. Vavilov’s research is his theory of homological series. 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 the known variations of characters in a well-studied species are arranged in a certain order, then in other related species one can find almost all the same variations in the variability of characters. For example, the variability of the ear awn is approximately the same in soft, durum wheat and barley.

Interpretation by N.I. Vavilov. Species and genera genetically close are characterized by similar series of hereditary variability, with such regularity that, knowing the number of forms within one species, one can foresee the finding 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 evolutionarily closer compared taxa. The homology of genes in related species is manifested in the similarity of the series of their hereditary variability (1987).

The Significance of the Law

1. The law of homological series of hereditary variability makes it possible to find the necessary characters and variants in an 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 traits. This is the enormous practical significance of the law for crop production, animal husbandry and selection.



3. Its role in the geography of cultivated plants is comparable to the role of the Periodic Table of Elements of D. I. Mendeleev in chemistry. By applying the law of homologous series, it is possible to establish the center of origin of plants by related species with similar characters and forms, which probably develop in the same geographical and ecological setting.

Ticket 4

Inheritance of traits during the divergence of sex chromosomes (primary and secondary non-disjunction of the X chromosomes in Drosophila)

As noted earlier, when a white-eyed female Drosophila is crossed with a red-eyed male in F1 all daughters have red eyes, and all sons who receive their only X- a chromosome from the mother, eyes are white. However, sometimes in such a crossing, 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 due to the fact that during meiosis, both X chromosomes in their mother fell into one egg, i.e. there was a nondisjunction X-chromosome. Each of these eggs can be fertilized either by sperm X- a chromosome, or Y-chromosome. As a result, 4 types of zygotes can be formed: 1) with three X- chromosomes - XXX; 2) with two mother X- chromosomes and Y-chromosome XXI; 3) from one paternal X-chromosome; 4) without X- chromosomes, but Y-chromosome.

XXI are normal fertile females. XO- male, but sterile. This shows that Drosophila Y The chromosome does not contain sex-determining genes. When crossing XXI females with normal red-eyed males ( XY) Bridges found among the offspring 4% of white-eyed females and 4% of 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 the secondary nondisjunction X-chromosomes in meiosis, because females taken in crossing ( XXY), arose due to the primary nondisjunction of chromosomes. Secondary nondisjunction of chromosomes in such females during 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 descendants resulting from non-divergence X-chromosomes in women, individuals that do not have any X chromosomes are lost during embryonic development. Zygotes XXX develop in women who are more likely to have mental defects and infertility. From zygotes XXI defective men develop - Klinefelter's syndrome - infertility, mental retardation, eunuchoid physique. Descendants from one X-chromosome often die in embryonic development, rare survivors are women with Shereshevsky-Turner syndrome. They are short, infantile, barren. In man Y-chromosomes contain genes that determine the development of the male organism. With absence Y-Chromosome development proceeds according to the female type. Sex chromosome nondisjunction occurs more frequently in humans than in Drosophila; on average, for every 600 boys born, there is one with Klinefelter's syndrome.