| Genetic Engineering |
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| Contributed by Ria Roo | ||
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A number of human diseases are the result of individuals being unable to produce for themselves chemicals which have a metabolic role. Many such chemicals, e.g. insulin and thyroxine, are proteins and therefore the product of a specific portion of DNA. The treatment of deficiencies previously involved extracting the missing chemical from either an animal or human donor. This has presented problems. While the animal extracts may function effectively, subtle chemical differences in their composition have been detected by the human immune system, which has responded by producing antibodies which destroy the extract. Even chemically compatible extracts from human donors present a risk of infection from other diseases, as the tranmission of the HIV virus to haemophiliacs illustrates only too well. Whether from animals or humans, the cost of such extracts is considerable. The part of the DNA molecule which specifies a polypeptide is termed a gene. Perhaps the most significant scientific advance in recent years has been the developement of technology which allows genes to be manipulated, altered and transferred from from organism to organism - even to transform DNA itself. This has enabled us to use rapidly reproducing organisms such as bacteria as chemical factories producing useful, often life saving substances. The listof these substances expands almost daily and includes hormones, antibiotics, interferon and vitamins. The Manipulation of DNA involves three main techniques , each using a specific enzyme or group of enzymes: Cutting of DNA into small sections using restriction endonucleases. These enzymes are used to cut DNA between specific base sequences which the enzyme recognises. For example, Hae III nuclease recognises a four base pair sequence and cuts it transversally. Production of copies of DNA using either plasmids or reverse transcriptase. In bacterial cells there are small circular loops of DNA called plasmids. plasmids are distinct from the large circuar portions of DNA which make up the bacterial chromosome. Bacteria replicate their plasmid DNA so that a single cell contains many copies. If a portion of DNA from, say, a human cell, is inserted into a plasmid and it is reintroduced into the bacterial cell,, replication of hte plasmid will result in up to 200 identical copies of hte human DNA being made. Joining together portions of DNA using DNA ligase. The recombination of pieces of DNA, e.g. the addition of cDNA The 'c' stands for carrier) into bacterial plasmid DNA, is carried out with the aid of the enzyme DNA ligase. Now you have some background understanding, we can discuss some of the potential harm and benefits of Genetic Engineering (GE) Firstly, a common concern with the production of virulent genes with multi resistance to anti biotics will be accelerated. If such virulent genes combine with the genes of harmful viruses to form new viruses, it will be disastrous for humankind. GE also reduces biodiversity. The nutritional level of our food depends on this diversity. In the long term, GE may lead to the destruction of the human food supply. At present there is no evidence that GE protein and GE food is detrimental to human health, but the possibility of harm cannot be eliminated. To develope potentially harmful food when ther e is an adequate supply of natural food is not a wise thing to do. However, for the first time in human history, scientists it is possible to make multiple copies of any existing organism or of certain sections of its genetic structure. This ability to clone existing organisms or their genes gives scientists a very powerful tool to reproduce helpful and useful genetic material within a population. Scientists are also developing techniques to treat and cure genetic diseases through genetic surgery and genetic therapy. They can already identify genetic sequences that are defective , and soon scientists will be able to replace these defect with properly functioning genes. This means cure's for 1000's of incurable diseases, such as Parkinson's, cystic fibrosis and thalidamide related mutations. Scientists will also have the ability to scan a person's DNA to see if they are susceptible to a disease, and prevent the DNA from mutating later in life, or replacing the DNA with the correct base sequence. All in all, as many potential hazards and problems with GE, it could also solve a lot of our problems if we dont jump the gun and the ethical barriers surrounding it. Only registered users can write comments.
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