Artificial Mutagenesis in Animal Breeding
Subject: Genetics, reproduction, selection
Question 1. List the methods of breeding.
The main selection methods include selection, hybridization, polyploidy, artificial mutagenesis.
Artificial selection – the selection by a person of the most economically valuable individuals of animals and plants in order to obtain offspring from them with desirable characteristics. Artificial selection is the most important breeding method and the main factor behind the variety of domestic animal breeds and cultivated plant varieties.
Hybridization – a natural or artificial crossing of individuals that differ in their characteristics and belong to different varieties, breeds, strains, species. Hybridization produces hybrids.
Hybrids are formed by combining the hereditary material of genotypically different organisms and are characterized by new traits or new combinations thereof.
In breeding, organisms belonging to different species or even genera are also crossed. In these cases, distant hybridization takes place – a rather complicated process, since organisms belonging to different species, and even more so to different genera, have different genetic material (the number and structure of chromosomes). Very often, such a cross leads to the formation of sterile (sterile) hybrids that do not produce offspring. However, thanks to the painstaking work of breeder scientists, intergeneric hybrids capable of reproducing have been obtained.
Artificial mutagenesis is a selection method based on the effect on organisms of mutagens that cause various mutations. Based on these mutations, new varieties and strains are often created. As mutagens, ultraviolet and X-ray irradiation, exposure to neutrons or chemicals are usually used. Artificial mutagenesis is especially widely used in the development of new strains of microorganisms.
Polyploidy is the production of polyploids, i.e. organisms in which the number of chromosomes is increased by two, three or more times. This process is carried out by acting on a dividing cell by various factors that interrupt the divergence of chromosomes to the poles. As a result of the action of chemicals, ionizing radiation, high or low temperature, cell division is impaired, and it becomes, for example, tetraploid (4p). Polyploids have higher yields, are richer in nutrients and are more resistant to adverse environmental factors.