genetic engineering

The genetic modification of a bacterium to produce insulin. The human gene for the production of insulin is collected from a donor chromosome and spliced into a vector plasmid (DNA found in bacteria but separate from the bacterial chromosomes). The plasmids and recipient bacteria are mixed together, during which process the bacteria absorb the plasmids. The plasmids replicate as the bacteria divide asexually (producing clones) and begin to produce insulin.

All-inclusive term that describes the deliberate manipulation of genetic material by biochemical techniques. It is often achieved by the introduction of new DNA, usually by means of a virus or plasmid. This can be for pure research, gene therapy, or to breed functionally specific plants, animals, or bacteria. These organisms with a foreign gene added are said to be transgenic (see transgenic organism) and the new DNA formed by this process is said to be recombinant. In most current cases the transgenic organism is a micro-organism or a plant, because ethical and safety issues are limiting its use in mammals.

The breakthrough in this field came in 1973, when two biologists at the University of California succeeded in the recombination of two pieces of DNA from organisms that would not reproduce naturally. By the end of the 1970s, scientists were able to add genes to mice to create the first genetically modified (GM) mammal. They also were able to add human genes to bacteria and put this technology to commercial use in manufacturing human proteins for drugs. By early 1995 more than 60 plant species had been genetically engineered, and nearly 3,000 transgenic crops had been field-tested.

In 1998 27.8 million hectares of land in the USA was planted with genetically engineered crops. More than two-thirds of this land grew herbicide resistant crops, mostly soybeans and maize. In 2002, the growth rate of planting these GM crops was 3.8 million hectares or 10% per annum. By 2003 the USA grew 42.8 million hectares of GM crops, 63% of the world's total amount.

The process of genetic engineering involves several steps: the formation of DNA fragments, the insertion of DNA fragments into a vector plasmid, cloning of the plasmid, use of the plasmid to introduce the DNA into the organism, and expression of the gene.

One example of genetic engineering that has been very helpful to humans is the production of bacteria that make human insulin - the bacteria were engineered to contain the human gene for insulin. The bacteria are cultivated in fermenters to produce large amounts of insulin, which is then used to treat diabetic patients (see diabetes). Prior to this, people with diabetes were treated with insulin from other animals. This new procedure removes the need to kill animals for insulin, and in addition the engineered insulin works better.

Practical uses In genetic engineering, the splicing and reconciliation of genes is used to increase knowledge of cell function and reproduction, but it can also achieve practical ends. Gene splicing was invented in 1973 by the US scientists Stanley Cohen and Herbert Boyer, and patented in the USA in 1984. Examples of its use include giving plants grown for food the ability to fix nitrogen - this would have a huge impact on world food production. It could be achieved by the introduction of genes that allow plants to live with bacteria in their roots that make nitrogen fertilizer. This occurs naturally with plants such as clover, peas, and beans, but not with crops such as wheat, maize, or rice. The requirement for expensive fertilizers would be greatly reduced.

It is also possible to introduce genes into crops that give resistance to pests and herbicides. Between 1996 and 2003, herbicide tolerance was the dominant trait required of GM crops. In 2003, herbicide-resistant cotton, soybean, canola, and maize accounted for 49.7 million hectares, or 73% of the global GM crop.

Genetic engineering could also increase the nutritional quality of foods and extend shelf life. It may be possible in the future to use transgenic animals in, for example, the production of ‘designer milk’ - milk containing human antibodies for the treatment of disease or low cholesterol milk, which might improve human health.

Simple bacteria may be modified to produce rare drugs. A foreign gene can be inserted into laboratory cultures of bacteria to generate commercial biological products, such as synthetic insulin, hepatitis-B vaccine, and interferon.

Genetic engineering can be used in disease diagnosis by the use of gene probes or engineered antibodies to identify if a person has a particular gene connected with disease.

Dangers of genetic engineering Despite all the benefits, potential and real, there are good arguments that suggest that there are possible dangers in genetic engineering. In addition there are moral and ethical views that argue against genetic engineering in principle.

Science cannot help to make decisions about the moral and ethical issues. However, potential dangers can be studied scientifically; these include the accidental production of new disease-causing micro-organisms, the spread of herbicide and pest resistance genes into wild plants, and food safety issues.

Steps are being taken to ensure that these problems will not occur, but there is still debate about their effectiveness.

New developments Developments in genetic engineering have led to the production of growth hormone, and a number of other bone-marrow stimulating hormones. New strains of animals have also been produced; a new strain of mouse was patented in the USA in 1989 (the application was rejected in the European Patent Office). A vaccine against a sheep parasite (a larval tapeworm) has been developed by genetic engineering; most existing vaccines protect against bacteria and viruses.

The first genetically engineered food went on sale in 1994; the ‘Flavr Savr’ tomato, produced by the US biotechnology company Calgene, was available in California and Chicago.

By 2004, scientists had developed a range of gene targeting techniques that allowed them to select where in a chromosome they could place a piece of foreign DNA. These procedures significantly increase the options available to genetic engineers, allowing the addition, alteration, or removal of genes at will.

Safety measures There is a risk that when transplanting genes between different types of bacteria (Escherichia coli, which lives in the human intestine, is often used) new and harmful strains might be produced. For this reason strict safety precautions are observed, and the altered bacteria are disabled in some way so they are unable to exist outside the laboratory.

There are also concerns for the environmental consequences of genetically modified crops and in 1999 US ecologists found evidence that maize modified to contain the insecticidal genes from the soil bacterium Bacillus thuringiensis may be harmful to the monarch butterfly caterpillar. Monarchs feed on milkweed, which often grows near maize fields and some of the transgenic maize pollen is contaminating the milkweed.