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Video: Inbreeding - Pro Et Contra
This article is addressed to those cat lovers and owners of cat kennels, as well as the chairmen of those clubs and associations who set their main goal to consolidate and improve the breed qualities of their animals through purebred breeding and selection (selection). We emphasize right away that since selection implies strict culling, this goal comes into conflict with commercial breeding of cats, where the main goal is profit.
British shorthair kitten
Inbreeding as a component of purebred breeding
In the course of his work, the breeder must decide which females with which selected males should be mated so that their offspring combine certain traits and acquire improved traits. This breeding event is called cross-breeding. The selection of pairs should be carried out systematically and systematically, and the purpose of it is to change the genetic structure of the animal population of a given nursery in the desired direction or to preserve and consolidate a certain combination of valuable traits in the offspring. Sometimes, to breed new breeds or introduce completely new traits into a breed that were not previously characteristic of it, interbreed or even interspecific crossbreeding is used, but usually the main direction of the breeder's work is the so-called purebred breeding - mating individuals of the same breed.
Related article Purebred cats: medical, breed and genetic aspects
Purebred breeding is divided into two types: outbreeding is a system of unrelated mating of animals within a breed, and inbreeding is a system of mating of individuals with a close degree of kinship, such as brother-sister, father-daughter, mother-son, cousins, etc. In general, inbreeding assumes that the mating individuals - the future father and mother - have common ancestors or at least one common ancestor. Although the importance and necessity of inbreeding in purebred breeding is obvious to specialists, there are many myths and prejudices among amateurs, both against inbreeding itself and against the use of inbred sires in breeding. (Let's say in advance that the latter is a particularly big mistake, since inbred selective sires are, as a rule, prepotent - their children turn out to be mostly "fatherlike" - and also often produce extremely strong offspring.)
Genetic rationale for inbreeding
What is the biological (genetic) essence of inbreeding? All modern animal breeds, including cats, are heterozygous for many genes. This means the following. The zygote - a fertilized egg - receives from both the father and the mother one complete set of genes, so it has a double set of them. If both genes responsible for a given trait - one from the father and the other from the mother - are identical, then this condition is called homozygous for this gene, and an individual homozygous for this gene will develop from the egg. If the genes equivalent pairs, for example, determine the formation of black pigment of hair are different (for example, father passed black C gene, and the mother - a modified example Himalayan gene s), then the individual is heterozygous for a given turn gene (Cc s). In the latter case, the black gene dominates, and the animal externally (phenotypically) will turn out black, but will be the carrier of the recessive (hidden) Himalayan gene. If such a heterozygous animal - let it be a black cat, a carrier of the Himalayan gene is crossed with his own sister, also a black cat carrying a hidden Himalayan gene, then splitting will be observed in the offspring: part of the offspring will be black (CC - homozygous, and Cc s - heterozygous genotypes), and the other part is of the Himalayan (with s with shomozygous genotype), This is because when this black cat is crossed with his black sister, their gamete germ cells (sperm and egg) - carrying a single set of genes, will be found in all four possible combinations: C from a cat and C from a cat, C from the cat and with s from the cat, with s from the cat and C from the cat, with s from the cat and with sfrom the cat. Consequently, with a 1/4 probability, two Himalayan genes (one from the father, the other from the mother) will converge in one zygote and give a homozygous Himalayan genotype and, therefore, a Himalayan phenotype in some of the litter kittens. Another part of the litter, with the same 1/4 probability, will be homozygous for the solid black gene (CC). Thus, the genetic essence of inbreeding is reduced to the process of decomposition of a population on a line with different homozygous genotypes, since during inbreeding genes that were in a heterozygous state go into a homozygous state, in the next generation, when crossing homozygous animals of the same color, no cleavage will be observed. In this way, with the help of inbreeding, hidden traits are identified, the desired traits are fixed in generations and the creation of stable genetic lines.