.. nbound probe, and placed over a piece of x-ray film. When developed, the film reveals the location of the radioactivity as a black spot. The corresponding colony on the original plate thus contains the bacteria carrying the required gene. The applications of genetic engineering are vast, probably the most well known is gene therapy in the medical world. It involves the introduction of a gene into somatic cells and enablement of its products to alleviate a disorder caused by the loss or malfunctioning of a vital gene product. Involving the latest DNA technology, it is the most rapidly advancing form of molecular medicine, which is concerned with the cause of disease at a molecular level.
The scope for gene therapy has increased over in the last few years with the possibility of a therapeutic gene for diseases such as cancer, AIDS, cystic fibrosis, and even neurological disorders such as Parkinson’s disease and Alzheimer’s disease. The potential of gene therapy to treat specific human diseases, has hardly become apparent yet but it is believed be the way forward in the treatment of many diseases. Trials in United States are being carried out in an attempt to treat AIDS. The strategies are in the form of a treatment which will protect susceptible cells from infection by the virus once it is in the body, or to inhibit the replication of HIV in already affected cells. Moreover to try to boost the immune response to HIV and HIV-infected cells. This and many other diseases have become to show potential of being treated in this fashion.
Gene therapy has resulted in the possible reduction in cancerous tumours. Tumours in lung cancer patients shrunk or stopped growing when scientists inserted healthy genes into to replace defective or missing genes, it demonstrated that by correcting a single genetic abnormality in lung cancer cells may be enough to slow down or stop the spread of cancer. Further research into the use of gene therapy to cure or help cancer victims has been continued after the discovery of this method. As well as in medicine there are many applications of genetic engineering in agriculture. Genetically engineered hormones are available, and may be used in the future to increase meat or milk yields of livestock.
Soon disease may be wiped out with the use of genetically engineered vaccines. Fertilisers may become obsolete, as scientists attempt to introduce ntirogenase genes into plants, the gene coding for the enzyme that catalyses the breakdown of atmospheric nitrogen. Plants could also in theory be able to produce their own insecticides thus making artificial ones obsolete. Crops could even be engineered to grow in naturally inhospitable areas and could effectively make food shortages a thing of the past. Recently, genetic technology has shown that it will affect our everyday lives, such as in the grocery store. There has been work in the growing of genetically engineered foods.
The government has even approved the sale of certain products. The nutritional value can be increased, as well as the hardiness of crops. Another interesting idea is that of transgenic animals. Transgenic technology bypasses conventional breeding by using artificially constructed parasitic genetic elements as vectors to multiply copies of genes, and in many cases, to carry and smuggle genes into cells that would normally exclude them. (Parasites, by definition, require the host cell’s biosynthetic machinery for replication.).
Once inside cells, these vectors slot themselves into the host genome. In this way, transgenic organisms are made carrying the desired transgenes. The insertion of foreign genes into the host genome has long been known to have many harmful and fatal effects including cancer; and this is borne out by the low success rate of creating desired transgenic organisms. Typically, a large number of cells, eggs or embryos have to be injected or infected with the vector to obtain a few organisms that successfully express the transgene(s). The most common vectors used in gene biotechnology are a mosaic recombination of natural genetic parasites from different sources, including viruses causing cancers and other diseases in animals and plants, with their pathogenic functions’crippled’, and tagged with one or more antibiotic resistance ‘marker’ genes, so that cells transformed with the vector can be selected.
For example, the vector most widely used in plant genetic engineering is derived from a tumour-inducing plasmid carried by the bacterium Agrobacterium tumefaciens. In animals, vectors are constructed from retroviruses causing cancers and other diseases. Unlike natural parasitic genetic elements that have varying degrees of host specificity, vectors used in genetic engineering are designed to overcome species barriers, and can therefore infect a wide range of species. Thus, a vector currently used in fish has a framework from the Moloney murine leukaemic virus, which causes leukaemia in mice, but can infect all mammalian cells. It has bits from the Rous Sarcoma virus, causing sarcomas in chickens, and from the vesicular stomatitis virus, causing oral lesions in cattle, horses, pigs and humans.
Genetic fingerprinting is a well-known application of genetic engineering, it is often used in an aid to identify the perpetrator of a crime. This is possible because everyone (except identical twins) has a unique genetic fingerprint. The process was developed by Alecs Jeffreys at the University of Leicester in 1984. He noticed that there were unusual sequences in DNA that seemed out of place. These sequences (minisatellites) are repeated many times throughout DNA. A DNA probe is used to analyse these patterns.
A DNA probe is a synthetic length of DNA made up of a repeated sequence of bases. This is cloned to make a batch of probes using the recombinant DNA into E. Coli bacterium technique. A radioactive label is then attached by exchanging all the phosphate molecules with radioactive isotopes of the same species. The DNA which is to analysed is then fragmented using a restriction enzyme, placed on agarose gel and the fragments separated using a process called electrophoresis.
Fragments of DNA have negative charges, so when and anode is placed at the other end of the gel, the DNA is attracted to it. The distances they move are dependent on the size of the fragment, with the lighter, shorter fragments moving the furthest. Once they are separated, the fragments are transferred to a nylon membrane are treated with the DNA probe. These bind to any complementary minisatellite sites, and make them show up on x-ray film because of the radioactivity. The pattern of bands revealed is known as the DNA fingerprint.
This would seem fail safe, but there are many problems associated with this technique. Samples taken from the victim’s body will more than likely have the victims DNA as well, not to mention any bacterial or fungal DNA present. Dyes used in clothes can also alter restriction enzymes, making them fragment in the wrong place. DNA fingerprinting is therefore not infallible. People rightly fear that what they eat could harm them if it has been gene altered.
It is also quite possible that products can be made safer and less allergenic than before this new technology. If food can be grown more economically as a product of gene technology, world hunger can be virtually stamped out. It is feared by some people that we might knock nature off balance by interfering with it. There is no possible way that it could truthfully be said that we haven’t done so already. Ever since we discovered how to make fire, we have defeated nature’s balance.
It does not take genetic medicine to increase our populations beyond what natural barriers had been in place, such as disease and famine. When the possible threats and the potentially helpful applications are weighed it appears that research into the possibilities should continue. If people’s fears of what can be done wrong were to stop the industry it still would not insure that in the future the technology won’t be used in such a way. If future governments really wanted to they could rediscover it and use it immorally, regardless of what we do now. Scientists should learn how to use it safely and responsibly now so that, hopefully, future scientists will do the same.
The current ethic followed by genetic scientists does not allow genetic manipulation in human embryos. Lack of knowledge does keep scientists wary of what they are doing in human genetics. However, their caution is somewhat less with other animals. Genetic engineering has and will undoubtedly provide the means to help mankind. But we must consider whether it is socially or ethically desirable.
Along with technology must go an ethical evaluation. Early trials with growth enhanced pigs revealed disastrous side-effects for the animals.