Anjam Naz
Genetic Engineering
Genetic engineering is the artificial alteration of the genetic code. It is often described as a very precise method of changing the genetic makeup of an organism.
Genes are a definite sequence of bases in the DNA chain which together code for the production of a particular protein. They are sections of the DNA which control traits of an individual, such as eye colour, which are different for each person. By natural breeding genes are passed down to offspring by the parents however, with new technology scientists are able to identify an individual gene and insert it into another organism which will then carry the trait of that gene. This alters the DNA. The extraction of the gene is done by physical and chemical methods
The process of moving a gene from one molecule to another molecule is called cloning. In the cloning process a fragment of DNA, containing a gene is cloned into a vector where it is grown in large quantities and manipulated in a variety of ways. The most common vectors are bacterial plasmids but viruses and self-replicating units in eukaryotic cells are also employed as vectors.
To carry out genetic engineering the source DNA and vector DNA need to be isolated, and they must be free of any contamination as they may interfere with the remaining processes, the DNA's are cut using restriction enzymes. The vector and source DNA are mixed together using a ligase system and are covalently bonded together. The ligand DNA is now ready to be transformed into a host cell.
If for example, the nutritional quality of rice was being improved by adding to it a gene that increases its lysine content, lysine is an amino acid which is in short supply in most plants. Then firstly DNA from a high-lysine plant is extracted, one with a gene that enhances lysine production from a plant such as a daffodil which is a lysine rich plant. Then using the enzymes that cut DNA, the high-lysine gene is removed from the rest of the daffodil DNA and is inserted into the plasmids. These plasmids that are carrying the daffodil gene ...
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If for example, the nutritional quality of rice was being improved by adding to it a gene that increases its lysine content, lysine is an amino acid which is in short supply in most plants. Then firstly DNA from a high-lysine plant is extracted, one with a gene that enhances lysine production from a plant such as a daffodil which is a lysine rich plant. Then using the enzymes that cut DNA, the high-lysine gene is removed from the rest of the daffodil DNA and is inserted into the plasmids. These plasmids that are carrying the daffodil gene are allowed to infect a culture of bacterial cells. The cells which have succeeded in aquiring a plasmid with the daffodil gene are identified and grown as a pure cell culture. The culture becomes a clone of identical genes carrying the daffodils high lysine gene. The gene is now ready to be transferred into the cell. To introduce the daffodil gene into a plant, a method is needed which will allow it to penetrate through the plants thick cell wall. Infection is the easiest route, infectious plant plasmids can be used to carry the gene if the plant accepts the plasmid. Some plants can accept such plasmids easily, however, the rice will not. Therefore, the technique used is; shooting the daffodil DNA into cells of rice plants with a particle gun. To load the gun the high lysine daffodil DNA is coated onto tiny gold pellets. When the gun is fired a burst of high pressure helium gas slams a DNA coated pellet through the thick plant cell wall and into the interior of the cell. The hole is so small that the cell is not hurt. Once inside the cell the injected DNA dissolves from the pellet and combines with the cells own DNA. The cells which have successfully received a pellet are selected and developed into adult rice plants.
There are many other useful applications of genetic engineering. It is possible to insert human genes into sheep so they secrete alpha-1-antitypsin in their milk, which helps to treat lung cancer.
A DNA test has been designed which detects pigs that are carriers of a genetic mutation that causes Porcine Stress Syndrome, which affects the quality of the meat. Also, there is cloning, which is a branch of genetic engineering where the genetic material of an organism is duplicated. Ian Wilmut discovered that in the body of a mature adult, the cells "switch-off" the genes not relevant to their function. He found a way to reactivate these genes and grow a completely new organism from this.
In 1997, Dolly the Sheep was the first adult mammal cloned. In the future, it may be possible to make a 'twin' of yourself, or to make 'improvements by identifying the gene that wants altering.
The Human Genome Project, which is funded by the US Government, plans to identify the entire human genome. Its aim is to treat genetic disorders, such as Downs Syndrome and Cystic Fibrosis. This is called gene therapy. Research on the human genome can be done on aborted fetuses.
In genetic engineering there are many ethical issues. Many people disagree with genetic engineering because it is unnatural. It may seem like the scientists are just 'playing God'. some people also say that it is unethical to clone as life should be a precious gift from God.
Another problem with genetic engineering is that there is no way of knowing the long term effects and weather it is safe or not. There may be problems with future generations. Genes in transgenic plants could 'escape' into other species, for example a herbicide resistant crop could cross-pollinate with weeds making them herbicide resistant. There may also be economic problems for example with genetically modified crops, it may result in developed countries no longer needing crops from developing crops, therefore resulting in loss in trade.
People who can afford it can pay for gene therapy, however, those who cant will not be bale to pay for it, so isn't really fair on those who cant afford it.
With cloning, there are many ethical problems, but also psychological problems, for example a clone of someone who has died may be difficult for the family to deal with. The clone is still a human being, and it may be difficult for them also, especially if they have to live up to the expectations of their original.
Biotechnology has indeed contributed to human understanding and welfare, however, it's far too soon to celebrate as involves the manipulation and transformation of life at its most fundamental levels. If used improperly, its consequences could be devastating. Genetic engineering has few limits, except our imagination, and our personal morals. Genetic engineering will be inevitable, which will be difficult to adjust to, but will the long-term effects be for the best?
Bibliography
Bown, T.A. Gene Cloning, 3rd Edition
www.gene-watch.org/
Parker, John. LETTS Revise AS biology, Revision Guide
www.geneticengineering.org/
Barry, Alberts, Lewis, Raff, Roberts, Watson, Molecular Biology of the Cell, Third Edition
