Mutations that occur naturally without the influence of various factors on the body are called spontaneous. The main feature of the manifestation of spontaneous mutations is that genetically close species and genera are characterized by the presence of similar forms of variability. The pattern of the presence of homologous series in hereditary variability was established by the outstanding geneticist and breeder, Academician N.I. Vavilov (1920). He revealed that homologous series exist not only at the species and genus levels in plants, but can also be found in mammals and humans.
The essence of the law is that genetically close genera and species are characterized by homologous (similar) series in hereditary variability. Similar genotypic variability is based on a similar genotype in closely related forms (i.e., a set of genes, their position in homologous loci). Therefore, knowing the forms of variability, for example, a number of mutations in species within one genus, we can assume the presence of the same mutations in other species of a given genus or family. Similar mutations in genetically related species N.I. Vavilov called homological series in hereditary variability. Examples:
1) representatives of the cereal family have a similar genotype. Within the genera of this family (in wheat, rye, oats, etc.), similar mutations are observed. These include the following: bare grain, awnless, lodging, different consistency and color of grain, etc. Awnless forms of wheat, rye, oats, and rice are especially common;
2) similar mutations occur in humans and mammals: short-toed (sheep, humans), albinism (rats, dogs, humans), diabetes mellitus (rats, humans), cataracts (dogs, horses, humans), deafness (dogs, cats, humans ), etc.
The law of homological series of hereditary variability is universal. Medical genetics uses this law to study diseases in animals and develop methods of treating them in relation to humans. It has been established that oncogenic viruses are transmitted through germ cells, integrating into their genome. In this case, the offspring develop co-diseases similar to the parents. The sequence of nucleotides in DNA has been studied in many closely related species, and the degree of similarity is more than 90%. This means that the same type of mutations can be expected in related species.
The law has wide application in plant breeding. Knowing the nature of hereditary changes in some varieties, it is possible to predict similar changes in related varieties by influencing them with mutagens or using gene therapy. This way you can bring about beneficial changes in them.
Modification variability(according to Ch. Darwin – a certain variability) – these are phenotypic changes under the influence of environmental factors that are not inherited, and the genotype remains unchanged.
Changes in phenotype under the influence of environmental factors in genetically identical individuals are called modifications. Modifications are otherwise called changes in the degree of expression of a characteristic. The appearance of modifications is due to the fact that environmental factors (temperature, light, moisture, etc.) affect the activity of enzymes and, within certain limits, change the course of biochemical reactions. Modification variability is adaptive in nature, in contrast to mutational variability.
Examples of modifications:
1) arrowhead has 3 types of leaves, differing in shape, depending on the action of the environmental factor: arrow-shaped, located above the water, oval - on the surface of the water, linear - immersed in water;
2) in the Himalayan rabbit, in place of the shaved white fur, when placed in new conditions (temperature 2 C), black wool grows;
3) when using certain types of feed, the body weight and milk yield of cows increase significantly;
4) lily of the valley leaves on clay soils are wide, dark green, and on poor sandy soils they are narrow and pale in color;
5) dandelion plants moved high to the mountains, or to areas with a cold climate, do not reach normal sizes and grow dwarf.
6) if there is an excess potassium content in the soil, plant growth increases, and if there is a lot of iron in the soil, then a brownish tint appears on the white petals.
Modification properties:
1) modifications can occur in a whole group of individuals, because these are group changes in the severity of symptoms;
2) the changes are adequate, i.e. correspond to the type and duration of exposure to a certain environmental factor (temperature, light, soil moisture, etc.);
3) modifications form a variation series, therefore they are classified as quantitative changes in characteristics;
4) modifications are reversible within one generation, i.e., with a change in external conditions in individuals, the degree of expression of characteristics changes. For example, in cows, with a change in feeding, milk yield may change; in humans, under the influence of ultraviolet rays, a tan, freckles, etc. appear;
5) modifications are not inherited;
6) modifications are adaptive in nature, i.e., in response to changing environmental conditions, individuals exhibit phenotypic changes that contribute to their survival. For example, pet rats adapt to poisons; Hares change seasonal colors;
7) are grouped around the average value.
Under the influence of the external environment, to a greater extent, the length and shape of leaves, height, weight, etc. change.
However, under the influence of the environment, signs can change within certain limits. Reaction rate– these are the upper and lower limits within which the characteristic can change. These limits within which the phenotype can vary are determined by the genotype. Example 1: milk yield from one cow is 4000–5000 l/year. This indicates that variability of this trait is observed within such limits, and the reaction rate is 4000–5000 l/year. Example 2: if the height of the stem of a tall oat variety varies from 110 to 130 cm, then the reaction norm for this trait is 110–130 cm.
Different signs have different reaction norms - broad and narrow. Wide reaction rate– leaf length, body weight, milk yield of cows, etc. Narrow reaction norm– fat content of milk, color of seeds, flowers, fruits, etc. Quantitative traits have a wide reaction rate, while qualitative traits have a narrow reaction rate.
Statistical analysis of modification variability using the example of the number of spikelets in an ear of wheat
Since modification is a quantitative change in a characteristic, it is possible to perform a statistical analysis of modification variability and derive the average value of modification variability, or variation series. Variation series variability of the trait (i.e., the number of spikelets in the ears) - arrangement of ears in a row in increasing number of spikelets. The variation series consists of individual options (variations). If you count the number of individual variants in a variation series, you can see that their frequency of occurrence is not the same. Options ( variations) is the number of spikelets in ears of wheat (a single expression of the trait). Most often, the average indicators of the variation series are found (the number of spikelets varies from 14 to 20). For example, in 100 ears of corn, you need to determine the frequency of occurrence of different variants. The calculation results show that the most common ears are those with an average number of spikelets (16–18):
The top row shows the options - from smallest to largest. The bottom row is the frequency of occurrence of each option.
The distribution of variants in a variation series can be shown visually using a graph. The graphical expression of the variability of a characteristic is called variation curve, which reflects the limits of variation and the frequency of occurrence of specific variations of a trait (Fig. 36) .
V
Rice. 36 . Variation curve of the number of spikelets in an ear of wheat
In order to determine the average value of modification variability of wheat ears, it is necessary to take into account the following parameters:
P – number of ears with a certain number of spikelets (frequency of occurrence of the trait);
n – total number of variant of the series;
V – number of spikelets in an ear (variants forming a variation series);
M – the average value of modification variability, or the arithmetic mean of the variation series of wheat ears, is determined by the formula:
M=–––––––––– (average value of modification variability)
2x14+7x15+22x16+32x17+24x18+8x19+5x20
M=––––––––––––––––––––––––––––––––––––––––––––––– = 17, 1 .
The average value of modification variability has practical application in solving the problem of increasing the productivity of agricultural plants and animals.
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.
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.
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 discovered 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.
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.
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.
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.
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.
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.
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.
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.
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.
In 1920 N.I. Vavilov outlines the main ideas of the Law of Homologous Series in a report at the III All-Russian Selection Congress in Saratov. Main idea: related plant species have similar spectra of variation (often a fixed number of strictly defined variations).
“And Vavilov did such a thing. He collected all the known hereditary characteristics from the best studied, as I already said, plants from among the cultivated cereals, arranged them in a certain order in tables and compared all the subspecies, forms and varieties known to him at that time. A lot of tables were compiled, of course, there was a huge amount of material. At the same time, back in Saratov, he added legumes to cereals - various peas, vetches, beans, beans, etc. - and some other cultivated plants. And in many cases there was parallelism in many species. Of course, each family, genus, and species of plants had their own characteristics, their own form, their own way of expression. For example, the color of seeds varied from almost white to almost black in almost all cultivated plants. This means that if better studied cereals with a huge number of already known, studied varieties and forms have several hundred different characteristics described, but other, less studied or wild relatives of cultivated species do not have many characteristics, then they can, so to speak, be predicted. They will be found in the corresponding large material.
Vavilov showed that, in general, the hereditary variability of all plants varies to a very large extent in parallel. He called this the homologous series of plant variability. And he pointed out that the closer the species are to each other, the greater the homology of the series of character variability. A number of different general patterns have been identified in these homologous series of hereditary variability in plants. And this circumstance was taken by Vavilov as one of the most important foundations for further selection and search for economically useful traits in plants introduced into cultivation. The study of homologous series of hereditary variability, first of all in cultivated plants, then in domestic animals, is now self-evident, one of the foundations for further selection of varieties of certain types of plants being studied that are needed by humans. This was, perhaps, one of Vavilov’s first major achievements on a global scale, which very quickly created his worldwide name. The name of, if not the first and best, then one of the first and best applied botanists in the world.
In parallel with this, Vavilov made a large number of expeditions around the world - throughout Europe, most of Asia, throughout much of Africa, North, Central and South America - collecting enormous material, mainly on cultivated plants. In 1920, I think, Vavilov was made director of the Bureau of Applied Botany and New Crops. This Bureau was slightly changed and turned into the Institute of Applied Botany and New Crops, then the Institute of Applied Botany, Genetics and Plant Breeding. And by the end of the 30s it had already become the All-Union Institute of Plant Growing. This name has still been preserved, although its global share, of course, fell greatly after the death of Vavilov. But still, many Vavilov traditions are still maintained, and part of the huge world living collection of varieties, subspecies and forms of cultivated plants from literally all groups of plants cultivated on the globe is preserved in Pushkin, the former Detskoye Selo, the former Tsarskoe Selo. This is a living museum, replanted every year, created by Vavilov. The same is true at countless experimental stations scattered throughout the Soviet Union.
During his numerous trips, Vavilov again managed not to drown in the enormous material, in this case the geographical diversity of forms of various types of cultivated plants. He plotted everything on large-scale maps with multi-colored pencils, first playing with geographic maps like little children, and then translating it all into relatively simple small maps with black icons of various types for different forms of cultivated plants. So he discovered in the world, on the globe, in the biosphere of our planet, several centers of diversity of cultivated plants. And he showed, simply on maps, the spreading, distribution on Earth not only of individual species, but of certain groups of species, domesticated, apparently, for the first time in a certain place, well, say, in Northern or Central China or in the mountainous part of North Africa, or , say, in the region of Peru, in South America, in the mountains, in the Andes. From there, usually not just one species of some cultivated plant, but a group of economically related species that arose as cultivated plants and took root as cultivated plants in a certain place, spread across the Earth. Some are not far, a short distance, while others have conquered half the world, as they say, like the same wheat or peas.
Vavilov thus established centers of diversity and origin of various forms of cultivated plants in different places on the globe. And he created a whole theory of the origin of cultivated plants in various eras of the ancient and ancient world. This was Vavilov’s second great achievement, again a worldwide one. Now it is impossible to further develop the history of world agriculture and the history of the centers of origin of cultivated plants without the foundation created by Vavilov. There are attempts, so to speak, at some reform and modification of Vavilov’s views, but we can say that these are particularities in comparison with the general world picture created by Vavilov.
This means that I have already listed three huge achievements: plant immunity, the law of homological series and the theory of agricultural centers and the emergence of various forms of cultivated plants. Perhaps the last thing I would like to name from Vavilov’s general achievements is a large number of his works and efforts, mainly efforts in the sense of propaganda at various congresses, international and all-Union, writing popular science articles on the problem of promoting agriculture to the north in the first place and in areas occupied by deserts and wastelands, combined with nature conservation in a completely modern and even intended for the near future sense: the promotion of culture together with a reasonable attitude towards the communities of living organisms of the biosphere. In these areas, Vavilov is absolutely exceptional, I would say, an exceptionally great scientist on a global scale.”
Homologous series in hereditary variability- concept introduced N. I. Vavilov when studying parallelisms in the phenomena of hereditary variability by analogy with homologous series organic compounds.
Law of homologous series: Genetically close species and genera 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.
Patterns in polymorphism in plants, established through a detailed study of the variability of various genera and families, can be conditionally compared to some extent with the homologous series of organic chemistry, for example, with hydrocarbons (CH 4, C 2 H 6, C 3 H 8 ...).
The essence of the phenomenon is that when studying hereditary variability in close groups of plants, similar allelic shapes that were repeated in different species (for example, straw knots cereals With anthocyanin with or without coloring, ears of corn With awn or without, etc.). The presence of such repeatability made it possible to predict the presence of yet undiscovered alleles that are important from the point of view breeding work. The search for plants with such alleles was carried out on expeditions to the supposed centers of origin of cultivated plants. It should be remembered that in those years artificial induction mutagenesis chemicals or exposure ionizing radiation was not yet known, and the search for the necessary alleles had to be done in natural populations.
N.I. Vavilov considered the law he formulated as a contribution to the ideas popular at that time about the natural nature of variability underlying the evolutionary process (for example, the theory nomogenesis L. S. Berg). He believed that hereditary variations that naturally repeat in different groups underlie evolutionary parallelisms and phenomena mimicry.
In the 70-80s of the 20th century he turned to the law of homological series in his works Mednikov B. M., who wrote a number of works in which he showed that precisely this explanation of the emergence of similar, often down to the last detail, characters in related taxa is quite valid.
Related taxa often have related genetic sequences that are slightly different in principle, and some mutations occur with a higher probability and manifest themselves generally similarly in representatives of different, but related, taxa. As an example, a two-variant phenotypically pronounced mutation in the structure of the skull and the body as a whole is given: acromegaly And acromicria, for which a mutation that changes the balance, timely “switching on” or “switching off” during the ontogenesis of hormones is ultimately responsible somatotropin And gonadotropin.
The doctrine of the centers of origin of cultivated plants was formed on the basis of the ideas of Charles Darwin (“The Origin of Species,” Chapter 12, 1859) about the existence of geographic centers of origin of biological species. In 1883, A. Decandolle published a work in which he established the geographical areas of the initial origin of the main cultivated plants. However, these areas were confined to entire continents or other fairly large territories. Within half a century after the publication of Decandolle's book, knowledge in the field of the origin of cultivated plants expanded significantly; Monographs were published on cultivated plants from various countries, as well as individual plants. This problem was most systematically developed in 1926-39 by N. I. Vavilov. Based on materials about the world's plant resources, he identified 7 main geographic centers of origin of cultivated plants.
1. South Asian tropical center (about 33% of the total number of cultivated plant species).
2. East Asian center (20% of cultivated plants).
3. South-West Asian center (4% of cultivated plants).
4. Mediterranean center (approximately 11% of cultivated plant species).
5. Ethiopian center (about 4% of cultivated plants).
6. Central American center (approximately 10%)
7. Andean (South American) center (about 8%)
Centers of origin of cultivated plants: 1. Central American, 2. South American, 3. Mediterranean, 4. Central Asian, 5. Abyssinian, 6. Central Asian, 7. Hindustan, 7A. Southeast Asian, 8. East Asian.
Many researchers, including P. M. Zhukovsky, E. N. Sinskaya, A. I. Kuptsov, continuing the work of Vavilov, made their own adjustments to these ideas. Thus, tropical India and Indochina with Indonesia are considered as two independent centers, and the South-West Asian center is divided into Central Asian and Western Asian; the basis of the East Asian center is considered to be the Yellow River basin, and not the Yangtze, where the Chinese, as a farming people, penetrated later. Centers of ancient agriculture have also been identified in Western Sudan and New Guinea. Fruit crops (including berries and nuts), having wider distribution areas, go far beyond the centers of origin, more consistent with the ideas of De Candolle. The reason for this lies in its predominantly forest origin (and not in the foothills as for vegetable and field crops), as well as in the peculiarities of selection. New centers have been identified: Australian, North American, European-Siberian.
Some plants were introduced into cultivation in the past outside these main centers, but the number of such plants is small. If previously it was believed that the main centers of ancient agricultural cultures were wide valleys Tiger, Euphrates, Ganga, Nila and other large rivers, Vavilov showed that almost all cultivated plants appeared in the mountainous regions of the tropics, subtropics and temperate zones. The main geographical centers of the initial introduction into culture of most cultivated plants are associated not only with floristic richness, but also with ancient civilizations.
It has been established that the conditions in which the evolution and selection of a crop took place impose requirements on the conditions of its growth. First of all, this is humidity, day length, temperature, and duration of the growing season.
MUTATIONAL VARIABILITY
Plan
Difference between mutations and modifications.
Classification of mutations.
Law of N.I.Vavilov
Mutations. The concept of mutation. Mutagenic factors.
Mutations – are sudden, permanent, natural or artificial changes in genetic material that occur under the influence of mutagenic factors .
Types of mutagenic factors:
A) physical– radiation, temperature, electromagnetic radiation.
B) chemical factors – substances that cause poisoning of the body: alcohol, nicotine, formaldehyde.
IN) biological- viruses, bacteria.
The difference between mutations and modifications
Classification of mutations
There are several classifications of mutations.
I Classification of mutations by meaning: beneficial, harmful, neutral.
Useful mutations lead to increased resistance of the organism and are material for natural and artificial selection.
Harmful mutations reduce vitality and lead to the development of hereditary diseases: hemophilia, sickle cell anemia.
II Classification of mutations by localization or place of occurrence: somatic and generative.
Somatic arise in the cells of the body and affect only part of the body, while mosaic individuals develop: different eyes, hair coloring. These mutations are inherited only during vegetative propagation (in currants).
Generative – occur in germ cells or in the cells from which gametes are formed. They are divided into nuclear and extranuclear (mitochondrial, plastid).
III Mutations by the nature of the genotype change: chromosomal, genomic, gene.
Genetic (or point) not visible under a microscope, are associated with changes in gene structure. These mutations occur as a result of nucleotide loss, insertion, or substitution of one nucleotide for another. These mutations lead to gene diseases: color blindness, phenylketonuria.
Chromosomal (perestroika) associated with changes in chromosome structure. What may happen:
Deletion: - loss of a section of a chromosome;
Duplication – doubling of a chromosome segment;
Inversion – rotation of part of the chromosome by 180 0;
Translocation – exchange of sections of non-homologous chromosomes and merger two non-homologous chromosomes into one.
Causes of chromosomal mutations: the occurrence of two or more chromosome breaks followed by their joining, but in the wrong order.
Genomic mutations lead to a change in the number of chromosomes. Distinguish heteroploidy And polyploidy.
Heteroploidy associated with a change in the number of chromosomes, on several chromosomes – 1.2.3. Reasons: non-disjunction of chromosomes in meiosis:
- Monosomy – decrease in the number of chromosomes by 1 chromosome. The general formula of the chromosome set is 2n-1.
- Trisonomy – increase in the number of chromosomes by 1. General formula 2n+1 (47 chromosomes Clanfeiter syndrome; trisonomy of 21 pairs of chromosomes - Down syndrome (signs of multiple congenital defects that reduce the vitality of the body and impaired mental development).
Polyploidy – multiple change in the number of chromosomes. In polyploid organisms, the haploid (n) set of chromosomes in cells is repeated not 2 times, as in diploid ones, but 4-6 times, sometimes much more - up to 10-12 times.
The occurrence of polyploids is associated with a violation of mitosis or meiosis. In particular, non-divergence of homologous chromosomes in meiosis leads to the formation of gametes with an increased number of chromosomes. In diploid organisms, this process can produce diploid (2n) gametes.
Widely found in cultivated plants: buckwheat, sunflower, etc., as well as in wild plants.
N.I. Vavilov’s law (law of homologous series of hereditary variability).
/ Since ancient times, researchers have observed the existence of similar characteristics in different species and genera of the same family, for example, melons, similar to cucumbers, or watermelons, similar to melons. These facts formed the basis of the law of homological series in hereditary variability./
Multiple allelism. Parallel variability. A gene can exist in more than two states. The diversity of alleles of one gene is called multiple allelism. Different alleles determine different degrees of the same trait. The more alleles individuals in a population carry, the more plastic the species is, the better adapted to changing environmental conditions.
Multiple allelism underlies parallel variability - a phenomenon in which similar characters appear in different species and genera of the same family. Systematized the facts of parallel variability N.I. Vavilov./
N.I. Vavilov compared species of the Cereals family. He found out that if soft wheat has winter and spring forms, awned and awnless, then the same forms are necessarily found in durum wheat. Moreover, the composition of features. By which forms differ within a species and genus, it often turns out to be the same in other genera. For example, the forms of rye and barley repeat the forms of different types of wheat, forming the same parallel or homologous series of hereditary variability.
Systematization of facts allowed N.I. Vavilov to formulate law of homologous series in hereditary variability (1920): species and genera that are genetically close are characterized by similar series of hereditary variability with such regularity. That, knowing a number of forms within one species, one can predict the presence of parallel forms in other species and genera.
The homology of hereditary characters of closely related species and genera is explained by the homology of their genes, since they originated from the same ancestor species. In addition, the mutation process in genetically close species proceeds similarly. Therefore, they develop similar series of recessive alleles and, as a result, parallel traits.
Conclusion from Vavilov's law: each species has certain boundaries of mutational variability. No mutation process can lead to changes that go beyond the spectrum of hereditary variability of the species. Thus, in mammals, mutations can change the color of the coat from black to brown, red, white, stripes and spotting may occur, but the appearance of a green color is excluded.
