In the 1970s people suffering from diabetes mellitus used insulin from cattle pigs, but this was expensive time consuming. Moreover insulin from other animals was not exactly as same as those in humans, causing many side-effects. Also many people were against the use of animal insulin for ethical or religious reasons. This problem had to be solved & in 1970's biotechnological companies began working of genetically modifying a bacterium to produce insulin by insertion of a human gene. many different methods were tried & tested, then finally in the early 1980's they suceeded, this was agreat achievement in the science world. the procedure was as follows :-
Isolation of insulin gene
insulin is a small protein . the first challenge was to isloate the insulin gene from the rest of the DNA in the human cell. But there was a problem doing so directly, instead the mRNA carrying the code for synthesizing insulin was extracted from the cells in the pancreas that produces insulin, called B-cells.
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then the mRNA was left in incubation with reverse transcriptase, reverse transcriptase is a special retrovirus, it does the opposite of transcription i.e codes for DNA from RNA, this newly coded DNA is called complimentary DNA or simply cDNA. at first single stranded molecules were formed, which then turned in double helix. these DNA molecules carried the code for human insulin. these DNA molecules then needed to be stuck to other DNA strands, & so they were given sticky ends by adding lenghts of single stranded DNA made up of guanine nucleotide to each end using enzyymes.
insertion of gene into a vector
for the human insulin gene to be inserted into a bacterium, there has to be an intermediate carrier of the gene called a vector & this was a plasmid. plasmids are small circular pieces of DNA found in many bacteria. plasmids can freely move into bacterium cells and if we are able to insert the human DNA inside the plasmid & then insert plasmid into a bacterium. To obatin the plasmids from the bacteria containing them, these bacteria frist had to be mixed with enzymes to dissolve their cell walls. then centrifuged so that large organelles e.g chromosomes & small ones like plasmids would be seperated. restriction enzymes were used to slice open the the circular DNA making up the plasmid. sticky ends were added again but this time the nucleotide used to make them conatined cytosine & guanine bases on their ends paired up. DNA ligase was then used to link the nucleotide backbone together so that the human insulin gene became part of tthe plasmid. this was the manufacture of recombinant DNA.
Advantages of treating diabetes by human insulin
There are a number of advantages of using the human insulin produced by genetically engineered bacteria:
it is chemically identical to the insulin that would have been produced had they not been diabetic, so there is little chance of an immune response
because it is an exact fit in the human insulin receptors in human cell surface membranes, it brings about a much more rapid response than pig or cow insulin,
like natural human insulin, the duration of the response is much shorter than pig or cattle insulin,
it overcomes problems related to the development of a tolerance to insulin from pigs or cattle,
it avoids any ethical issues that might arise from the use pig or cattle insulin, for example, religious objections to the use of pig insulin or objections from vegetarians to the use of animal products.
Benefits of gene technology
Through gene technology, it is now possible to produce:
â€¢ genetically modified organisms for a specific purpose. Previously, such genetic change would have to be brought about by selective breeding which requires organisms to be of the same species (able to breed successfully together), takes many generations and involves transfer of whole genomes, complete with undesirable background genes. Gene technology is much faster and involves transferring one or few genes, which may come from completely unrelated organisms, even from different kingdoms.
â€¢ specific products, such as human insulin and human growth hormone, thereby reducing the dependence on products from other, less reliable sources, such as pig or cow insulin.
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â€¢ reduce use of agrochemicals such as herbicides and pesticides since crops can be made resistant to particular herbicides, or can be made to contain toxins that kill insects
â€¢ clean up specific pollutants and waste materials - bioremediation
â€¢ potential for use of gene technology to treat genetic diseases such as cystic fibrosis (see below) and SCID (Severe Combined Immune Deficiency) as well as in cancer treatment.
Hazards of genetic engineering
Genes inserted into bacteria could be transferred into other bacterial species, potentially including antibiotic resistance genes and those for other materials, which could result in antibiotic resistance in pathogens, or in bacteria that can produce toxic materials or break down useful materials. Regulation is designed to minimise the risks of escape of such genes. There is little evidence that such genes have escaped into wild bacterial populations.
Crop plants have, by their nature, to be released into the environment to grow, and many millions of hectares of genetically engineered crops, both experimental and commercial, are planted across the globe. So far, fears that they might turn out to be 'super-weeds', resistant to herbicides and spreading uncontrollably, or that their genes might transfer into other closely related wild species, forming a different kind of 'super-weed', or that they might reduce biodiversity by genetic contamination of wild relatives seem to have proved unfounded. A paper was published in Nature in 2001 showing that Mexican wild maize populations were contaminated with genes from genetically manipulated maize, but the methods used were flawed and subsequent studies have not confirmed this contamination, suggesting that the wild maize is not genetically contaminated. There is some evidence that Bt toxin, geneticially engineered into plants such as cotton and maize, whilst very effective in killing the target species, may kill other, desirable, insects such as bees and butterflies, and may also cause natural selection of Bt toxin resistant insects. Future events may show that such environmental risks are greater than they look at present. Food that is derived from genetically engineered organisms may prove to be unexpectedly toxic or to trigger allergic reactions when consumed. There is little reliable evidence that this has been so, but the risk remains. Food containing the expressed products of antibiotic resistance marker genes could be consumed at the same time as treatment with the antibiotic was occurring, which would potentially reduce the effectiveness of the treatment. No examples of this are known.
social & ethical implocations of genetic engineering
ethics are set of rules set by people distinguishing between whats acceptable and whats not, between whats right and whats wrong. these ethics or rules change from a person to person depedning upon knowledge, experience, social influnce, religious influence etc.
The social impact of gene technology is to do with its potential and actual impact of human society and individuals. In terms of social impact, gene technology could:
â€¢ enhance crop yields and permit crops to grow outside their usual location or season so that people have more food
â€¢ enhance the nutritional content of crops so that people are better fed
â€¢ permit better targeted clean-up of wastes and pollutants
â€¢ lead to production of more effective and cheaper medicines and treatments through genetic manipulation of microorganisms and agricultural organisms to make medicines and genetic manipulation of human cells and individuals (gene therapy)
â€¢ produce super-weeds or otherwise interfere with ecosystems in unexpected ways, reducing crop yields so that people have less food
â€¢ increase costs of seed and prevent seed from being retained for sowing next year (by inclusion of genes to kill any seed produced this way) reducing food production
â€¢ reduce crop biodiversity by out-competing natural crops so that people are less well fed
â€¢ damage useful materials such as oil or plastic in unexpected ways
â€¢ cause antibiotics to become less useful and cause allergic reactions or disease in other unexpected ways
The ethical impact is about the application of moral frameworks concerning the principles of conduct governing individuals and groups, including what might be thought to be right or wrong, good or bad. So in the context of gene technology, it is to do with issues of whether is right or wrong to conduct research and develop technologies, whether it is good or bad. Judgements may be that
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â€¢ It is good to conduct such research to develop technologies that might improve nutrition, the environment or health
â€¢ It is good to use the results of such research to produce food, to enhance the environment or improve health
â€¢ It is wrong to continue such research when the potential impact of the technology is unknown and many aspects of it remain to be understood.
â€¢ It is wrong to use the results of such research even when the organisms are kept in carefully regulated environments such as sterile fermenters as the risks of the organisms or the genes they contain escaping are too great and unknown
â€¢ It is wrong to use the results of such research when this involves release of gene technology into the environment as once it is released it cannot be taken back - the genes are self-perpetuating, and the risks that they might cause in future are unknown
The social and ethical implications of gene technology are complex and relatively unfamiliar to people who are not scientists, including those involved in the media and in government. This complexity and unfamiliarity is the cause of considerable concern and debate. In considering the implications of gene technology the best approach is to avoid the general (e.g. avoid 'it is bad to play God') and stick to the specific and balanced (e.g. it is possible to increase food crop yields with gene technology so more people can be fed, but there is enough food already if it is properly distributed, so people should not be forced to eat products with unknown risks).