What do You Understand by Recombinant DNA Technology
There are two essential substances found inside bacterial cells required before the process can begin. Present in the cytoplasm of a bacterial cell are a number of small circular pieces of DNA known as plasmids. Also present within the bacterial cell are restriction enzymes which cut DNA molecules at specific sites. By selecting the correct restriction enzyme, DNA molecules from different organisms can be cut at predictable sites to extract specific genes from lengths of DNAi. The first task in the process is to isolate the required gene.
This can be done in three different ways; working backwards from the protein, using messenger RNA, or using DNA probes. Once the gene has been isolated, the next step is to cut the gene from its DNA chain. This is done using the restriction enzymes (restriction endonucleases). Now we have the required gene the next stage is to insert it into a vector which will be used to produce the required protein. This is where the plasmids described earlier come in (this could also be done using a virus as a vector).
The plasmid is cut using the same restriction enzyme as was used to cut the gene out. In a process called ligation (controlled by the ligase enzyme) the ends of the gene and those of the plasmid join together. The new molecule contains genes from the plasmid and from another organism and is thus called recombinant DNAii. This DNA is then introduced into the host cell and, using antibiotics the cells containing the recombinant DNA are selected. The genes which have been spliced into the vector continue to produce the same protein as they did in their original cells.
The vectors then multiply and produce many genetically identical daughter cells which also produce the required protein. There are many different methods of genetic engineering, but the outcome is the same, DNA from one species is inserted into a different species and made to produce its normal proteinsiii. ivFirstly I will consider the moral and ethical issues. It is hard to find any moral objection to the use of this technology in the treatment of diseases and improving food production. However, developing new therapeutic techniques may involve testing on animals.
A laboratory animal’s genes may be altered so that it suffers from a human genetic disease, and then they could be used to try out a new gene therapy which could be beneficial to humansv. Another ethical problem is the possibility of introducing favourable characteristics into human zygotes and thus creating “designer babies”. However, at present it is against the law to use genetic engineering in human gametes or embryos, so that recombinant DNA cannot be passed down through the generationsvi. Secondly, I am going to look at the social issues surrounding the technology.
There are many religious groups around the world who would have an objection to a specific transgenic organism. For example, to Hindus cows are sacred, and to Jews and Muslims pigs are unclean. The use of the genes of these organisms might be unacceptable to people from those religionsvii. Another religious objection that has been raised is against trivialising the act of the God in the creation of all the different species that inhabit the earth, and disrupting the divine planviii. Also, some fear that genetic screening may lead to discrimination against individuals.
For example, if a screened fetus was found to have a genetic disorder, the parents may decide to abort the pregnancy. Alternatively, adults found to have a gene predisposing them to a genetic disorder may be discriminated against by insurance companies and employers. Thirdly, I am going to consider the economic issues involved in the technology. Genetic manipulation has been presented as a way of feeding the world without damaging the environment. The use of genetic engineering could prove to be extremely economically rewarding.
For example, crop plants could be genetically altered to improve; their yield, their keeping properties, their taste etc. This would mean that more would be available, and they would last for longer, so more would be sold. It is also possible that crops could be altered to allow them to grow in a climate in which they would normally perish, or with extremely small amounts of water. This would allow third world countries to reap much better yields of good quality crops, and allow them to vastly improve their economy.
It is also hoped that the DNA responsible for the nitrogen fixing properties of bacteria could be introduced into crop plants, enabling them to fix atmospheric nitrogen and hence saving large amounts of money on fertilisersix. Another economic advantage could be found in altering the genes of oilseed rape. It may be possible to change the nature of the oils produced to make them more suitable for commercial processes. This could be used as a renewable source of oil when petroleum stocks run outx.
Another issue is that GM food may allow famine to be eliminated from the world as poorer countries will be able to produce more food that is suited to harsh climates. However, small farmers in poor countries may not be able to benefit from the research and sale of patented genes. Farmers in the US are already growing rapeseed plants which have been altered to produce tropical oils on which the economies of the Philippines and Indonesia dependxi. The final factor I am going to consider is environmental issues concerning the technology, of which there are many.
For example, if transgenic bacteria or viruses mutate, they may become new pathogens which we may not be able to controlxii. Also, genetically modified crops could escape resulting in genetically modified populations else where. If plants that were had a herbicide resistance characteristic escaped they may become weeds which we could not controlxiii. Populations of transgenic organisms might upset the balance of nature. For example, if a transgenic population which grew rapidly was produced it might compete for food with other species.
The latter could then become extinct and natural food webs would changexiv. It is also possible that genes which benefit one organism might reach other organisms in which they would be harmful. For example, if genes for herbicide resistance got into weeds the herbicides would become uselessxv. I mentioned above the possibility of introducing nitrogen fixing characteristics into crop plants. This brings in an environmental issue as well as an economic one, as the use of less fertilisers would reduce the problem of high nitrate levels in waterxvi.
Also, in order to identify cells which have taken up the foreign DNA antibiotic resistance genes are added as markers. This has raised fears over the spread of antibiotic resistance in animals and humansxvii. This new technology may also bring with it several unprecedented risks to our food. For example, the foreign genes enter the host DNA haphazardly and disrupt the region into which they are spliced which could affect cellular function. Alternatively, the transplanted genes unregulated production of foreign substances may upset complex biochemical feedback loopsxviii.
In conclusion, I think that there are many different issues surrounding the use of recombinant DNA technology. However, they all seem to come down to one basic fact. This is a very new technology, and we have not yet had time to learn what the repercussions of its wide spread use might be. The world’s leading scientists can sit an debate about the theory behind the technology until they are blue in the face, but with out putting it in to practice and seeing what happens we can never really know whether it’s safe. The question is however, are we willing to take the huge risks involved in finding out?
I think that the answer to this question has to be yes, otherwise we will be completely missing out on the opportunity to make use of something which could be a fantastically beneficial technology. However, I also think that if we are going to put the theory into practice on a large scale, we must ensure that genetically modified organisms pass through a stringent safety procedure. This procedure should involve intensive research into the answers to the following questions; how does the introduced gene affect the genetically engineered organism?
Is there any evidence suggesting that the introduced gene affects the toxicity of allergenic properties of the organism? Is there likely to be any unintended effects on other organisms within the environment? Is the genetically engineered organism likely to become a pest or pathogen or to invade natural habitats? Can the introduced gene be transferred to other organisms and if so what would be the likely consequences? I think that if all these safety regulations were strictly implemented then any of the negative issues surrounding the use of recombinant DNA technology will be outweighed by the positives.