Molecular Biotechnology: Principles and Applications - Glick B., Pasternak J. 2002

Molecular Biotechnology of Microbial Systems
Plant Genetic Engineering: Methodology

Until recently, high-yielding crop varieties and new animal breeds were developed through selective breeding. However, this time-consuming approach has given way to Methods based on the Introduction/32.html">Genetic Engineering OF higher organisms. Today, genes determining specific traits can be introduced into plant or animal Cells and transmitted to subsequent generations (inherited). In Part III, we will examine how such Transgenic Plants and animals are produced.

Several transgenic plant species have already been developed with traits determined by genes introduced via genetic engineering. These traits include The ability to synthesize insecticides, resistance to VIRAL INFECTIONS AND herbicides, altered fruit ripening times, modified flower coloration, enhanced Nutritional Value of seeds, and self-incompatibility. Research into animal transgenesis is still in its infancy, making it difficult to predict which genetic traits will be inherited by the recipient species. To date, transgenic mouse lines have been established and are used as model systems to study the Pathogenesis of Cancer, cystic fibrosis, Alzheimer's disease, and other human illnesses.

Recombinant DNA technology has found widespread application in The Study of inherited human diseases and The Development of Gene Therapy methods. For instance, by using a specific chromosomal site as a marker, a gene associated with a particular disease can be mapped to a human chromosome without any prior knowledge of its MECHANISM OF ACTION; subsequently, a cloned sequence that recognizes this marker site can be used to attempt to identify the defective gene. This approach has already led to the identification and characterization of genes responsible for several human diseases. Consequently, the Mechanisms of action of both normal and defective genes can be investigated to develop effective therapies. Part III discusses Human Molecular Genetics and gene therapy.

One of the primary goals of plant breeders has been to develop high-yielding crop varieties with enhanced nutritional value. While major emphasis was placed on cereal crops such as maize, wheat, and rice, breeding programs were also carried out for other agricultural and horticultural crops. Recombinant DNA technology, widely used in microbial systems, serves as an important tool for direct genetic modification of plants. To date, several efficient DNA delivery systems and expression vectors have been developed that function in various plant cells. A key advantage of plant cells is their totipotency: an entire plant can be regenerated from a single Cell, meaning that genetically engineered cells can yield fertile plants in which every cell carries the foreign gene(s) (transgenic plants). If such a plant flowers and produces viable seeds, the desired trait is transmitted to subsequent generations.

Three main arguments can be made in favor of developing transgenic plants. First, the Introduction of a gene (or genes) often enhances the agricultural value and ornamental qualities of cultivated plants. Second, transgenic plants can serve as living bioreactors for the low-cost production of economically important Proteins or metabolites. Third, plant genetic transformation (transgenesis) allows researchers to study gene action during plant development and other biological processes.

Certain genetically determined traits—such as insecticidal activity, resistance to viral diseases and herbicides, delayed senescence, tolerance to environmental stress, modified flower coloration, enhanced seed nutritional value, and self-incompatibility—can be acquired by a plant through the introduction of one or more genes. To date, numerous transgenic plants have been generated from both cultivated and wild species. Biotechnology will undoubtedly revolutionize traditional plant breeding programs, which typically require 10 to 15 years to develop a new variety. In the future, it will enable the creation of plants with entirely novel characteristics.