Genetic Engineering - How it is Used

What is Genetic Engineering?

Genetics is one of the most popular and has the largest potential subject which attracts many scientists devoted themselves to it nowadays. Genetic engineering which also known as genetic modification or recombinant DNA technology aims to change the inheritance of an organism. This artificial technology can change and amplify an organism’s genetic material in a way which can not be happened under natural conditions. It is an important branch of bioengineering. Today genetic engineering has gained a great achievement in many fields, such as agriculture, food, industry and medicine.

Genetic engineering is based on the theory of molecular genetics, and it is manipulated at the molecular level. With this technology, man can make breeding product among different species. Scientists calassified it to gene recombination on account of it can transfer foreign DNA to recipient cells through recombination in vitro. And vectors are needed in this transfer. Once foreign DNA fragment is inserted into a vector, the foreign DNA can duplicate, transcribe and translate in the host cells when they are injected into the host by physical or biological methods. In this way, different species can communicate between each other. Man can alter genetic material that they are interested in and produce new desirable characteristics in place of undesirable ones in one species. In this way, genetic engineering can contribute to food production promotion, antibiotics, vaccine, medical treatment and diagnose disease (Thomas, 2010).

How is genetic engineering performed? Producing a genetically modified organism is a multi-step process. It can be summarized in mainly four steps. They are isolation, construction, transfer, detection and expression.

Isolation

Firstly, the gene of interest should be selected and isolated. The two most common methods are shotgun method and artificial synthesis method. Shotgun method means that DNA which contains interesting genes will be cut into many pieces by restriction enzymes randomly, then these DNA fragments will be inserted into DNA vectors separately and these fragment carriers will then be transferred to host cells. After multiplication, the target DNA will be selected out.

Another way is synthesis by man based on RNA. The target DNA fragment can be artificially synthesized on the basis of two materials. If the donor is eukaryotic, RNA which is transcribed from the gene of interest is preferred to be selected. In this way, the RNA can be regarded as template to synthesis a new DNA; this process is called reverse transcription (Watson, 2007). This method can help people to get the interest genes. The other way is on basis of protein. If people know the amino acid sequence, then the nucleotide sequences in DNA can be deduced. After that, chemical methods will help to construct the target DNA.

Both two methods have advantages and disadvantages. Shotgun method is convenient to manipulate; however it also has the problem of a large amount of work. Artificially synthesized method has a higher accuracy. What is more, because eukaryotic gene has introns, this method is more popular used in target DNA isolation. However, this method is very difficult to control.

Construction

Now the target gene needs to be inserted into the vectors. Most vectors used today are plasmid and bacteriophages because of their great compatibility (Brown, 2006). This step is always completed with the help of restriction enzymes. Firstly, a restriction enzyme will cut the plasmid to give a gap, and the two ends of this gap are called sticky ends. Subsequently, the same restriction enzyme will be used to cut target DNA so that they will have the same sticky ends. After the cutting steps, the target gene product will be inserted into plasmid. The gap will joined by the means of DNA ligase. This product is called recombinant DNA. It is noteworthy that the chosen plasmid should have selectable marker so that it can be detected when they are in host.

Transfer

Once plasmid and target DNA cut connected together, now it is time to consider how to transfer it into host cells. There are many ways for transformation, such as electro injection, liposome-mediated transformation of protoplast and direct injection (Lichtenstein et al., 1987). Usually bacteria or virus infection are preferred to be used. For example, if the carrier is a plasmid and the recipients are bacteria, in this case, calcium chloride is chosen to be used firstly to help change the permeability of cell wall and carrier plasmid can infect into host easily by bacteria infection. Soon afterwards, the transferred plasmid will amplify in the host.

Detection and expression

Generally speaking, not all the target gene can be transformed into a new organism’s genetic material, therefore to know whether target genes have expressed in the host is a remarkable problem. One way to access to the results is special detection. In this case, a selectable marker is very useful to distinguish the transformed ones from untransformed cells. For instance, the plasmid of Escherichia coli has penicillin resistance genes, therefore transfected organisms can be differentiated after the plasmid transfer into host cells.

Genetic engineering is a great reform in human biological history. This technology contributes to many fields. In medicine production, protein-based drugs such as interferon and vaccines can be amplified a lot with this technology. In agriculture, many new characteristics have occurred in plants, for example, the viral-resistant plants, fast growing and large fruits amplification (Patterson, 1983). This technology also can be applied in industry. Nowadays, there is a kind of bacteria can decompose fossil oil which is called super bacteria. This bacterium has been made in America by genetic engineering, the scientists transfer different genes which can decompose different kind of oil into one bacterium and in this way super bacteria are produced (Levin et al., 1983)

It is can be concluded that genetic engineering is a kind of technology which can transfer foreign DNA from one specie to another cell. The first step is isolation, in this step the target gene can be chosen and isolated with the help of restriction enzyme. The second step is connection and target DNA will be inserted into vectors after this step. In the following, connection vectors will be transferred into host cells. Finally, the genetically modified organism will be detected out. Genetic engineering has been used in many areas now, and it is believed that this technology will be more glorious in the future.

References:

Brown, T.A. (2006), Gene Cloning & DNA Analysis an Introduction 5th edition. (Blackwell Publishing Ltd) Oxford, UK.

Levin, A.M., Kidd, G.H., Zaugg R.H. & Sware, J.R. (1983). Applied Genetic Engineering. (Noyes Publications), United States.

Lichtenstein, C.P., Fuller S.L., Lonsdale, D.M. & Messing, J. (1987). Genetic Engineering 6, (Peter W.J. Rigby. Eds.) Harcourt Brace Jovanovich Press, London.

Patterson, H.A. (1983), Genetic Control of Environmental Pollutants (Gilbert S. Omenn & Alexander Hollaender. Eds.), pp. 195-215. Plenum press, New York and London.

Thomas, S.V. (2010), Genome, genetic engineering and artifical cells. Annals of India Academy of Neurology, India.

Watson, J.D., Caudy, A.A., Myers, R.M. & Witkowski, J.A. (2007). Recombinant DNA genes and genomes-a short course. (Sara Tenney. Eds.) Cold Spring Harbor Laboratory Press, New York