Genetic Engineering

Genetic engineering, recombinant DNA technology, genetic modification/manipulation (GM) and gene splicing are terms that apply to the direct manipulation of an organism's genes.Engineering is different from traditional breeding, where the organism's genes are manipulated indirectly; genetic engineering uses the techniques of molecular cloning and transformation to alter the structure and characteristics of genes directly. Genetic engineering endeavors have found some success in improving crop technology, the manufacture of synthetic human insulin through the use of modified bacteria, the manufacture of erythropoietin in Chinese hamster ovary cells, and the production of new types of experimental mice such as the oncomouse (cancer mouse) for research.





Since a protein sequence is specified by a segment of DNA called a gene, novel versions of that protein can be produced by changing the DNA sequence of the gene.




Engineering




There are several ways through which genetic engineering is accomplished. Essentially, the process has four main steps:

1. Isolation of the genes of interest
2. Insertion of the genes into a transfer vector
3. Transformation of cells of organism to be modified
4. Separation of the genetically modified organism (GMO) from those that have not been successfully modified


Isolation is achieved by identifying the gene of interest that the scientist wishes to insert into the organism, usually using existing knowledge of the various functions of genes. DNA information can be obtained from cDNA or gDNA libraries, and amplified using PCR techniques. If necessary, i.e. for insertion of eukaryotic genomic DNA into prokaryotes, further modification may be carried out such as removal of introns or ligating prokaryotic promoters.





Insertion of a gene into a vector such as a plasmid can be done once the gene of interest is isolated. Other vectors can also be used, such as viral vectors, and non-prokaryotic ones such as liposomes, or even direct insertion using gene guns. Restriction enzymes and ligases are of great use in this crucial step if it is being inserted into prokaryotic or viral vectors. Daniel Nathans, Werner Arber and Hamilton Smith received the 1978 Nobel Prize in Physiology or Medicine for their isolation of restriction endonucleases.

Once the vector is obtained, it can be used to transform the target organism. Depending on the vector used, it can be complex or simple. For example, using raw DNA with DNA guns is a fairly straightforward process but with low success rates, where the DNA is coated onto particles such as gold and fired directly into a cell. Other more complex methods, such as bacterial transformation or using viruses as vectors have higher success rates.

After transformation, the GMO can be isolated from those that have failed to take up the vector in various ways.

Applications
The first genetically engineered medicine was synthetic human insulin, approved by the United States Food and Drug Administration in 1982. Scientists used bacteria in which they inserted plasmids containing the directions for insulin, they were then able to use the bacteria to produce and harvest artificial insulin. Another early application of genetic engineering was to create human growth hormone as replacement for a drug that was previously extracted from human cadavers. In 1987 the FDA approved the first genetically engineered vaccine for humans, for hepatitis B. Since these early uses of the technology in medicine, the use of GM has gradually expanded to supply a number of other drugs and vaccines. One of the best known applications of genetic engineering is the creation of genetically modified organisms (GMOs) such as foods and vegetables that resist pest and bacteria infection and have longer freshness than otherwise.

There are potentially momentous biotechnological applications of GM, for example oral vaccines produced naturally in fruit, at very low cost for most of the country.