Thursday, May 21, 2009

Understanding Genetic Transformation

The term genetically modified is frequently used to describe organisms that were genetically transformed or engineered. The science of genetic engineering was developed with the objective of building genes for genetic transformation. Genetic transformation systems possess three main components:

1) A mechanism for introduction of the foreign DNA into the target cell.

2) A cell or tissue suitable for transformation.

3) A method for the identification and selection of transformed cells or individuals.

Success in transformation for any species depends on these three components. Obviously, each one must be optimized and, therefore, as technology develops, transformation should become a more routine activity. The final objective in transformation is the introduction of a new trait in an individual. When the desired trait exists in any other sexually compatible individual, the first alternative should be to transfer the trait through crossing and selection, as has been done in conventional breeding since the 19th century. Modern soybean, corn, cotton, and wheat varieties, as well as swine, cattle, and poultry lines used in agriculture to feed the world, were initially obtained by traditional methods of crossing and selection.

One of the main limitations of conventional genetic improvement is that the breeder is limited to traits among species that are sexually compatible. For instance, the field bean is a species rich in sulfur-containing amino acids. However, beans are naturally deficient in lysine. On the other hand, rice is naturally rich in lysine, but deficient in sulfur-containing amino acids. It is not possible to naturally cross these species, so the conventional plant breeder is unable to develop a new field bean variety with elevated lysine levels or a rice cultivar rich in sulfur-containing amino acids. Genetic transformation allows the exchange of genes between organisms previously limited by sexual incompatibility. With genetic engineering and transformation, it is possible to transfer genes among bacteria, animals, plants, and viruses. In fact, one of the areas of research in biotechnology is the improvement of nutritional profiles in crops. New, more nutritional bean and rice varieties can now be developed through advances in genetic engineering.The basic tools for genetic transformation are restriction enzymes, which are used to cut DNA at specific sites, and ligases, which catalyze the joining of DNA fragments. Using the right restriction enzymes, it is possible to cut the circular bacterial plasmid DNA, causing it to linearize. With a ligase, it is possible to add other DNA fragments containing the gene of interest and join them to the linearized plasmid. Under the right conditions, the ends of the plasmid, now with the added DNA fragments, rejoin to create a new circular plasmid with some DNA modifications. The new plasmid can be introduced into certain bacteria through a process called electroporation, and the bacteria can then be used to transfer the transgene to the target species. If the plasmid DNA is integrated into the genome of the recipient species and the transferred genes are expressed, the individual is considered to be transformed or transgenic.

Tags: Bio Technology, Bio Genetics, Genetic Transformation

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