Реферат: Cloning And Genetic Engineering In The Food
Animal Industry Essay, Research Paper
When the Roslin Institute’s first sheep cloning work was announced in March 1996 the papers were full of speculation about its long-term implications. Because of this discovery, the media’s attention has focused mainly on discussion of the possibility, of cloning humans. In doing so, it has missed the much more immediate impact of this work on how we use animals. It’s not certain this would really lead to flocks of cloned lambs in the fields of rural America, or clinically reproducible cuts of meat on the supermarket shelves. But it does force us to ask questions about the way we are using animals with new technology, and the kinds of assumptions we make. To create Dolly (the cloned sheep), Scottish researchers simply took an unfertilized sheep egg and removed its genetic material. They then placed the empty egg in a dish with a cell from an adult sheep’s udder, which contained a full complement of the adult sheep’s genes. Finally the scientists applied an electric spark, which caused the two cells to fuse and begin dividing. The embryo was then transplanted into the womb of a surrogate mother to grow. The original aim of Dr Wilmut’s nuclear transfer work was to find better ways to make genetic modifications in animals, by growing live animals from cell culture. It is very possible that cloning was only a side effect of the investigation and not what was supposed to be the center of this research project. But the ability to clone opens up a range of questions of its own. We can already do it to a limited degree by splitting embryos, without ethical concerns. It has been practiced only to a very limited extent, mostly in cattle. At the moment there is only one set of results in one breed of sheep, and rather little is understood of how it has happened. Different farm animal species differ quite markedly in embryological interventions like artificial insemination and embryo transfer. So it remains to be seen whether this same method would work in any other animal, and without adverse effects. But assuming it could be applied more widely, what are the potential applications in animals? PPL (PPL Thearaputics Ltd, 1997) gives the example that it might be used, say, to clone 5-10 animals from a single genetically modified
animal. These would be bred naturally, thus becoming the “founders” of a set of lines of genetically modified animals from whose milk they would extract and purify the relevant protein.
But these medical applications tend to be small-scale affairs. The amount of animals and the amount of milk is very small compared with conventional meat or bulk milk production. Imagine you are a commercial breeder of cows or hogs, and over many generations you have bred some fine and valuable animals with highly desirable characteristics. One possible application of Roslin’s work could be to clone such animals from the cells of one of them, and sell the cloned animals to “finishers” – those farmers who simply feed up the animals for slaughter, rather than breed them to produce more stock. Again, the breeder might want to clone a series of fast growing, highly productive animals in a breeding program, in order to test how the same “genotype” responded to different environmental changes.
Would cloning narrow genetic diversity too far? Before we look at the ethics, there are some practical problems to consider. One of the fundamental rules of selective breeding is that you must maintain a high enough level of genetic variation. The more you narrow down the genetic “pool” to a limited number, the more you run two risks. One is that you could also have accidentally selected for some other not-so-desirable characteristic along with the one you wanted. (Klug, 1996) The selected lines could have certain disadvantages in some other genetic trait. These would be evened out in normal genetic diversity of selective breeding, but if animals were cloned, there would be no selection. The second risk is that a limited genetic pool is also much more vulnerable to having all its lines wiped by some virus or infection, as happened with the potato famine of Ireland, many years ago. (Klug, 1996) Supposedly, embryo freezing and gene banks could offset this, but the fact that this type of “gene storage” would need to be used indicates that we would be doing something wrong. (Morisson, 1996) Thus, I think that even animal production has its own limits on how far cloning would be worthwhile, as the Roslin Institute pointed out (Campbell, 1996).
Is cloning contrary to something fundamental about life? For the Christian, the world around us is God’s creation, filled with variety. Throughout the Bible, in commandments and stories, the overall theme is of diverse creation. I begin to wonder if we are not simply reducing ourselves to genetic blueprints. “The very fact that selective breeding has its limits reflects something about the need for natural diversity of things” (Basker, 1994). I do believe that cloning is acceptable in limited research, where the main intention was not the clone but rather growing an animal, where natural methods would not work. What would be unacceptable would be its use in routine production, where natural methods could be used but have been side-stepped on the bases of economics or convenience. What would be ethically wrong with this, you might ask, since we already intervene in nature with selective breeding? After all, we already selectively breed using methods like artificial insemination and embryo transfer. If there was a clear benefit to the farmer to start off with prime livestock, to produce the best beef or pork, this might be good. But raw food products have very little specialization and can not be separated on such a scale, making superior animals no more valuable than normal livestock. (Uhl, 1997)
What should we do with animals? Most of us eat them. Quite of a lot of us enjoy them as pets and companions, or watching some of them in the wild. But what else? Technology is now coming up with other ways of using the creatures we share this planet with. Recent developments in genetic engineering suggest we could use them as live “factories” for producing pharmaceuticals in milk or blood (PPL Theraputics Ltd., 1997), or growing organs for human transplants. Whatever use we find for animals, should we clone them so we can be more efficient? I have no problem with the use of livestock for food, but the fact that we kill animals to eat them seems to justify any other use. Why would we want to clone meat-producing animals, anyway? If the root is the supermarket production system, and the incentive of large meat contracts with the major chains, have we missed something important? To manipulate animals to be born, grow and reach maturity for sale and slaughter at exactly the time we want them seems to turn animals in mere commodity. Is this going too far in putting mass production allowing an animal the freedom to be itself. These are living things, which demand respect. Is cloning the point at which we should “hold back”? I would argue that the answer is “yes”, but these questions need the most careful scrutiny. And that raises another problem. How do we cope with these questions as a society?
How this work relates to Genetic Engineering
Cloning is not the same as genetic engineering. Genetic engineering modifies one or two genes amongst a mammal’s complement of about 100,000, to make a genetically new animal. Cloning copies the entire complement of genes, without modification, to produce a new individual animal that is genetically identical to its founder. But Roslin and PPL’s cloning discovery actually comes out of their existing genetic engineering work. Enhance the ability to do the type of genetic manipulations of animals In 1986 Roslin researchers made the ground-breaking discovery that it was possible to produce therapeutic proteins in the milk of sheep and other mammals by introducing one or two genes of human origin into the animal. This has since been developed into a wide set of potential medical applications. It is arguably the current leading example of genetic engineering in animals. The first protein to reach production by this means is alpha-1-anti-trypsin, which can counteract the lung damage found in emphysema and certain other diseases.
The first stage of clinical trials began in 1996. Successful as this has been so far, the present methods of doing this genetic engineering are very inefficient, and by nature rather hit and miss. The manipulation takes place in the laboratory cell cultures, and the resulting modified embryos are put back in the recipient animal, but so far it has not been possible to know which ones have got the right modification until each lamb is born. It can take a lot of animals before you have got one with the right gene in the right place. You could modify many sets of cells, select the ones which had the right modification, but the problem has been, up till now that no one had a way of growing a live animal from those cells.
Now Roslin and PPL have shown that you can grow a live sheep from cell cultures. This dramatic result opens the door to their next step – which will be to try it on genetically modified cells, to produce a genetically modified sheep, which has the modification in exactly the right place. If it works the method should allow a more precise manipulation with many less animals. Needless to say, careful scrutiny is needed, so that the only genetic manipulations this might be applied to would be ethically acceptable, but that is a question we already face. See our pages on The Ethics of Genetic Engineering? For more discussion of this issue. But the side effect of Roslin’s growing a sheep from cells is that the resulting sheep is a clone … and that could open the door to a lot of other uses, far beyond making pharmaceuticals in sheep, and possibly of disturbing ethical implications.
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