Genetics with the Fundamentals of Selection - M.P. Myhun - 2008

Chapter VIII. Genetic Foundations of Selection

8.6. Non-Traditional Methods of Selection

In the 1970s, the term "biotechnology" emerged to designate Methods used in the microbiological industry. Of course, biotechnology—as a set of industrial methods utilizing living cultures and biological processes—had existed long before (in baking, brewing, and The production of fermented dairy products). Over the past fifty years, microbiological synthesis of Antibiotics, Vitamins, Enzymes, and other substances has seen significant development. Today, biotechnological methods have been complemented by Gene and Introduction/32.html">Genetic Engineering techniques, which allow for the artificial creation of genetic material combinations and The formation of functionally active life forms.

The concepts of "genetic" and "gene" engineering are often used as synonyms, although the former is broader and encompasses methods of manipulating not only individual genes but also larger genome fragments, including entire Chromosomes.

Traditional Methods FOR generating initial breeding material (Hybridization, chemical and radiation mutagenesis...) are limited to the framework

of a specific species or closely related forms. Genetic engineering provides the opportunity to synthesize organisms with novel combinations of hereditary properties—often absent in nature—by combining genetic determinants from diverse sources within a single genome, including representatives of very distant species. Gene-engineering methods make it possible to obtain recombinant DNAs from genome fragments of various organisms, clone such artificially created molecules, introduce them into Cells using vectors (Plasmids or viral DNAs), and create conditions for the expression of these exogenously introduced, often entirely foreign genes within The Cell. Gene transfer from Cell to Cell at the DNA level and the generation of transgenic organisms can be independent of the taxonomic relationship of the organisms. This is the fundamental difference between gene engineering and traditional approaches to genotype restructuring.

The advantage of Genetic Engineering in this regard does not mean that its capabilities are boundless or that the artificial Introduction of a foreign gene into a genome instantly yields a new variety or breed. Artificial intervention in the genetic apparatus dramatically alters the overall gene balance, which in most cases reduces the viability and productivity of cells and organisms, or may result in the transplanted gene failing to function in a new genotypic environment.

Implementing any genetic engineering program involves the necessity of isolating DNA fragments carrying the desired gene; combining them in vitro with vector molecules capable of transferring the gene into recipient cells; and establishing conditions for the stable functioning and Inheritance of the transferred gene in a foreign genotypic environment. The successful resolution of these problems has been made possible by a series of developments in Molecular Genetics. Gene-engineering manipulations of hereditary material allow for the creation of fundamentally new starting material that requires further improvement through Selection.

The potential of Plant Genetic Engineering is vast, prompting scientists today to undertake breeding projects that seemed like science fiction until recently. One of the tangible successes of genetic engineering is the production of Transgenic Plants with altered traits that are resistant to insect pests (such as petunias, tobacco, corn, soy, potatoes, tomatoes, and cucumbers...), achieved even by introducing genes of animal origin into their genome. Another real success is the creation of genotypes resistant to herbicides. Successful experiments are underway to design and obtain transgenic plants with predictable properties. These include targeted modifications in the Amino Acid Composition of Proteins, early ripening, increased yield, and the creation of plant genotypes capable of utilizing atmospheric nitrogen, growing on saline soils, and resisting infectious agents, among others.

At present, the successes of gene-engineering research in animal subjects are considerably more modest, consisting mainly of cell transformation experiments.

At the same time, it should be noted that the PRACTICAL USE OF transgenic plants raises serious concerns among many geneticists and

ecologists. There are apprehensions that consuming genetically modified plants and products derived from them could prove harmful to animals and humans in the near or distant future, or disrupt the ecological balance in nature and complicate agricultural production. Despite the unique capabilities of Genetic engineering METHODS, their Structure/182.html">Practical Application must be approached with great caution and deliberation.

A significant contribution to generating Starting Material for breeding is modern cell technology based on in vitro somatic cell culture methods. The application of such technologies helps resolve A number of crucial problems in selection, namely:

1. Cloning — rapidly propagating valuable genotypes while bypassing the Fertilization process. This is based on the totipotency of somatic cell nuclei and was first accomplished in England in 1979. Today, it is widely used in veterinary practice. The propagation of plants via tissue and cell culture is called micropropagation. Currently, this propagation method is applied to more than 450 plant species. Methods have been developed to optimize conditions for all stages of such propagation: isolating a piece of plant tissue (explant), obtaining callus and shoots from it, rooting plant regenerants in vitro, and planting the regenerants in soil.

2. Obtaining virus-free planting material. This is based on using the apical meristem, which remains uninfected due to rapid Cell Division at the SHOOT apex. Such plants show a significant increase in productivity and product quality.

3. Expanding methods for propagating Higher Plant Cell masses to obtain valuable substances, such as ginseng Alkaloids or secondary metabolites. In this regard, cell-level selection aimed at obtaining the most productive cell clones is acquiring great importance.

4. Conducting cell-level selection utilizing somaclonal variation and artificial mutagenesis. Plant cells under in vitro conditions exhibit high genotypic Variability, known as somaclonal variation, which leads to The Emergence of cell clones with distinct cytogenetic parameters and to the spontaneous dominance of certain somaclones over others (autoselection). Artificial mutagenesis is also applied at THE CELLULAR LEVEL to accelerate the creation of modified genotypes.

5. Obtaining model objects to elucidate theoretical problems in genetics and selection (such as mechanisms of gene interaction).

6. Creating new genotypes through somatic (parasexual) hybridization of cells and protoplasts. Parasexual hybridization is based on the fusion of individual somatic cells or their protoplasts. By fusing cells and protoplasts of different origins, one can obtain: hybrid cells with combined genotypes of the parental cells; asymmetrical hybrids with unequal Genetic information from the predecessors; and cybrids—cell hybrids containing The Nucleus of one parent cell and the Cytoplasm of another. Vegetative plant forms have already been successfully regenerated from such hybrid cells.

Selective media are being developed for the selection of mutants and parasexual hybrids, which are used in research involving both PLANT AND ANIMAL cells.

The method of parasexual hybridization makes it possible to combine the genotypes of phylogenetically distant species that do not crossbreed in nature. For this reason, this cell technology, combined with genetic engineering methods, opens up new horizons for the Development of Genetics and breeding.