Fundamentals Of Dog Genetics

Fundamentals Of Dog Genetics
Fundamentals Of Dog Genetics

Video: Fundamentals Of Dog Genetics

Video: Fundamentals Of Dog Genetics
Video: Elaine Ostrander (NIH) 1: Canine Genetics: Dog Genes Tell Surprising Tales 2024, March
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Genetics is the science of heredity and variability of organisms. In the era of the scientific and technological revolution, genetics is one of the most relevant, rapidly developing branches of biology, always closely associated with practice.

On the basis of modern genetics, the microbiological industry is developing, in animal husbandry, selection and breeding are built on a genetic basis, human genetics is formed, the genetic foundations for preserving the integrity of the biosphere of the earth and near-earth space are developing.

Heredity is a property inherent in all organisms to transmit to posterity the characteristic features of the structure, individual development, metabolism, and, consequently, the state of health and predisposition to many diseases.

Sled with two Siberian huskies, dog photo photo
Sled with two Siberian huskies, dog photo photo

The transmission of traits from previous generations to offspring is called inheritance. The mechanism of this transmission is the process of reproduction, both during simple division of cells of protozoa and tissue cells, and during sexual reproduction, when the union of male and female reproductive cells (gametes) leads to the creation of a new organism that resembles parents and ancestors.

Variability - a property of organisms, the opposite of heredity, manifested in the dissimilarity of descendants with related generations. It is caused, on the one hand, by changes in the heredity of parental individuals, and, on the other, by the response of each organism to the effects of various environmental factors (climate, feeding, training, etc.). Some environmental factors, such as radiation, chemicals, viruses, can significantly change the hereditary substance of not only somatic (from the Greek soma - body) cells, but, more importantly, affect the heredity of germ cells, both of the parental generation and descendants. There is a chain of hereditary changes in the body called mutations. Mutational changes can be inherited and passed down through generations; this is the so-called hereditary variability,which is the main factor in the emergence of hereditarily determined new properties and characteristics.

Other environmental factors (feeding, climatic elements, etc.) cause changes in organisms that are not transmitted to offspring, that is, are not inherited, and are called modification variability. Under the influence of hereditary and non-hereditary variability in organisms, a complex of properties is formed, called phenotypic variability.

To carry out the correct selection of parental pairs, it is important to know and be able to determine and separate from phenotypic variability the share of the influence of hereditary and non-hereditary variability. The greater the share of the participation of heredity in the formation of the properties and characteristics of the organism, the more effective the breeding work.

The modern understanding of the mechanism of heredity is based on the characteristics of two types of nucleic acid molecules: DNA and RNA, which are part of cells. Nucleic acids have a filamentous structure of the molecule and are part of chromosomes - the main structures of the cell nucleus, and some RNA are also found in the cytoplasm. Separate sections of nucleic acid (DNA) strands form genes, which are a unit of heredity and control the possibility of the formation of a certain trait or property. Environmental factors either promote or inhibit the implementation of the gene's action and thereby affect the formation of the phenotype of the organism.

The main apparatus of heredity is the number and shape of chromosomes characteristic of each species. In the reproductive cell there are two times less of them (haploid number, symbol - n) than in any somatic cell, where they make up a double (i.e., diploid symbol 2 n) set of chromosomes in the form of pairs. Each pair includes chromosomes of the same size and shape. The set of paired chromosomes in a cell is called a karyotype. The number of pairs of chromosomes in karyotypes varies from 2 to 100 in different species. In dogs, the karyotype of bodily cells contains 78 chromosomes, that is, 39 pairs, and in each germ cell there is only a single set, consisting of 39 chromosomes.

The karyotype of an animal cell consists of several pairs of so-called autosomal chromosomes and one pair of sex chromosomes, denoted by the letters X and Y. Many animals are characterized by the presence of 2 sex chromosomes in addition to autosomes: for females - XX, and for males - XY. Therefore, in dogs, the karyotype of a bitch is 38 pairs of autosomes and a pair of XX chromosomes, and in a male - 38 pairs of autosomes and a pair of sex chromosomes XY. The transmission of hereditary traits occurs both through autosomes and through sex chromosomes. The latter determine the inheritance associated with the sex of the animal.

During fertilization in the offspring, 50 percent of females and 50 percent of males (Table 1) will be born from the combination of the XY chromosomes of the father's spermatozoa with the X - chromosomes of the gametes - of the female.

Thus, the mechanism of inheritance, that is, the transfer of various traits and properties, operates depending on the molecular structure of nucleic acids (DNA, RNA), their genetic composition. The process of transmission of these hereditary elements occurs through reproduction during the division of somatic cells and fertilization, in which the fusion of male and female gametes of sex cells leads to the formation of a new organism with a doubled set of chromosomal apparatus. The unit of inheritance is a piece of DNA called the genome. The gene of the father and the gene of the mother are called the alleles of the gene that determine a specific trait, and the DNA section in which the gene for this trait is located.

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