Inbreeding - what is it? Inbreeding: examples

The achievements of population genetics, its massive theoretical substantiation of all natural processes occurring in areas, allow people to use this knowledge in their own needs. So, such phenomena as inbreeding and outbreeding are very common. A more familiar synonym for these terms is incest. What are these processes from the scientific point of view and what can a person achieve by using them, we will analyze in this article.

Inbreeding - what is it?

First, let's define the concept. So, inbreeding, speaking in scientific genetic language, is the concentration of identical alleles of genes in a single genotype, that is, in a particular organism.

If in simple words to answer the question "Inbreeding - what is it?", It can be said that this is a purposeful crossing of closely related forms of plants, animals, people with the purpose of accumulating in the genotype certain alleles of the gene that carry the desired trait. In fact, there are several synonyms for this process. So, when it comes to the human population, closely related marriages are called incest. If we are talking about plants, then we are talking about insuhte. Inbreeding is a concept for animal husbandry. However, the same term can also be used in crop selection.

Heterosis

There is such a thing as an extreme degree of inbreeding. This happens when:

• The animal is capable of self-fertilization;
• The plant self-pollinates.

In these cases, to accumulate in generations homozygous alleles with the desired trait is much simpler, because the set of chromosomes from different individuals is excluded. This property is actively used in plant growing. Individuals from the first generation during self-pollination often give such results, at which the productivity rises by 60%! This is called heterosis and is the most widely used method of obtaining such products of plant origin, as:

• cotton;
• pepper;
• peas;
• Beans;
• citrus;
• wheat;
• Barley and others.

In inbreeding, carried out by a person, it is possible to extinguish the manifestation of harmful genes by translating them into a heterozygous state in future generations. This is done by artificial selection. If the plant lives in natural conditions, then such selection is carried out by nature itself, it is natural. That is why in nature among self-pollinating plants it is practically impossible to meet deformities, distortions and serious genetic diseases.

History of the concept development

If you plunge into history, then such a concept as incest exists since ancient times, since the time of the pharaohs. In different civilizations this phenomenon was perceived unequally. For example, in ancient Romans incest was considered a terrible sin. But in places like Egypt, the countries of Europe, pre-Columbian America, and all the adherents of paganism, this process was a perfectly normal component of life. The brothers freely married sisters, and this was welcomed, because it allowed to preserve the "noble" blood of the dynasty in the case of royal and royal families. However, the Bible forbade such incest, incest was considered to be the most terrible sin, therefore the entire Christian world stopped such processes with time.

If we talk about plants, animals, then about what inbreeding is, what is heterosis, people only learned with time through experience. It is clear that then the knowledge of population genetics was not available. People were guided only by visibility, by experienced trials. However, this was enough to be noticed: to obtain the necessary signs and fix them in the offspring, it is necessary to interbreed closely the closely related forms with the available gene, which is manifested externally.

The same applies to plants. It is known that as early as the 14th century, fine tulips of non-standard colors were grown in the Ottoman Empire, which were obtained through inksuhta. Among the animals, dogs were most often subjected to inbreeding, since they were the main attribute of hunting, and it, in turn, was practically the main entertainment.

Inbreeding in dogs made it possible to obtain the most powerful, hardy and well-trained hunting dogs. True, a large number of individuals that have arisen from mutations have been destroyed.

Degree and coefficient of inbreeding

Theoretical substantiations of the concept under consideration were given by many scientists, but the works of Englishman Wright and Russian Kislovsky are the most valuable. Together, but independently of each other, they have managed to create a formula that allows us to calculate the coefficient of inbreeding in generations. It looks like this:

F _x = Σ F (1/2) ^{n + ni-1} * (1 + F _a ) * 100, where

• F _x - coefficient of inbreeding, expressed as a percentage;
• F _a - Coefficient of inbreeding From a common ancestor;
• N, n _i - pedigree lines.

If you know several generations of a species, and also have information about the already calculated for ancestors coefficients of inbreeding, then you can calculate the indicator for any organism. Only it should be pointed out that such calculations are made only for a theoretical purpose. Practice shows that this method is inefficient, since it does not take into account recessive alleles carrying harmful mutations. And they can become both homo- and heterozygotes with frequent process runs.

Therefore, the results of practice differ from those calculated theoretically. Wright-Kislovsky's formula is used only when writing diploma theses, theses, dissertations, where a very large amount of data for many generations requires systematization and similar calculations.

If we talk about the degree of inbreeding, then we have already indicated it above. In the practice of dog breeding it is customary to designate it in Roman numerals, which show in what generation there was a common ancestor with the desired trait.

Classification

Close (close) inbreeding - what is it? This is one of the varieties of the process, which will be discussed below. Also, moderate and distant inbreeding is singled out. To understand the main differences and similarities between different species, consider each of them.

Close Inbreeding

This is the most complex and dangerous kind of this process. It consists in crossing the blood relatives of related species. If we translate into human degrees of kinship, then this is, for example, mother and son, father and daughter, brother and sister.

With this type of crossing, there is a close exchange of similar alleles. As a result, the desired sign is quickly manifested in the offspring of the first generation. However, it is dangerous that the resulting individual can carry a hidden recessive mutant gene, and there will be more of them, the larger the number of offspring. In such cases, accumulation of harmful symptoms occurs quickly and ugliness appears, stillbirth occurs, infertility of organisms.

Moderate appearance

Such inbreeding of animals is the crossing of more distant relatives. Translating to human degrees of kinship, these are, for example, cousins and sister, niece and uncle and so on.

As a result, it is possible to achieve homozygosity by the right parameters gradually, by making a careful selection. This process is long, but it minimizes the homozygosity of harmful alleles. As a result, you can get a good generation, strong, hardy and healthy in almost every litter.

Of course, the recessive allele of the mutant gene will still manifest itself, perhaps more than once, but eventually it will fade completely, going into a heterozygote.

Remote view

This inbreeding of animals implies the crossing of less closely related individuals. So, if you project on people, it can be, for example, second cousins and sisters.

Such a process gives the result is very weak, often almost imperceptible. In addition, studies have confirmed that over time generations of individuals with sharply negative signs appear. Animals are more painful, weak, mutant genes predominate and are the cause of deformities.

Obviously, getting the very best offspring that can convey its characteristics to the next generation and continue doing this down the chain is what inbreeding is aimed at (the purpose for which it is applied).

Examples of crossing

Inbreeding in animal husbandry has long been applied. And it is on the example of representatives of mammals that it is obvious how he works. Speaking about such inbreeding, examples can be given the following:

• Purebred horses;
• Clean lines of thoroughbred dogs;
• Species monotony of the necessary breeds of cats and so on.

In principle, it is possible to apply such a crossing to all kinds of animals. Just for most, it will be purely an experiment. But inbreeding, the examples of which we cited above, is already a task of serious practical importance.

Particularly great merit belongs to this experienced dog breeders, who know all the subtleties of crossing and getting a truly beautiful and healthy offspring. But genetics is a very capricious science, so there are blunders. Recessive genes can manifest themselves, and the individual will be unsuitable for sale, for the intended purpose, as a whole for life.

Inbreeding in cynology

As we have already noted, the cynologists are more devoted to the mysteries of the phenomenon in question than all other specialists. Inbreeding in dogs is an important condition for breeding purebred lines. Experienced breeders have proved that the most effective effect is provided by a moderate type of such crossing.

Conditions for successful inbreeding of dogs:

• Quality of the genotype of the ancestor;
• Competent and calculated approach to the process;
• Choice of a moderate option.

The main thing for any dog breeder is to prevent the onset of inbred depression. This is the state of the line when the individuals begin to transmit mutant genes that cause deformities to each other. As a result, all individuals are weak, painful and often die.

Outbreeding

Inbreeding in plant breeding is very important, because many crops are self-pollinated, so its effectiveness is high. But if we talk about animals, then more often apply outbreeding - the opposite in structure of the action. That is, not related relatives are crossed at all, as a result, they receive good thoroughbred lines. In this way, horses, cows, pigs, dogs and other pets are bred. Outbreeding is a simple and reliable method of breeding, since from generation to generation they receive stable offspring of productivity.