基因并非易於識別的，具體的物體。基因在生物體內的作用不單取決於脫氧核醣核酸（DNA）的次序，也包括它在某一特定染色體的、細胞的、生理的和進化的環境中所處的位置。因此，基因物質的轉換，對於一個複雜的生物體內，數以千萬計的結構和過程中，其間極度嚴密控製、整合、平衡的機能，所造成的衝擊是難以預測的。（註3）
基因工程是人工修改活的生物體的基因密碼。基因工程改變生物基本的物理性質，而有時改變的方式是在自然界中絕對不會發生的。一個生物的基因，往往是跨越自然品種的界限，而被植入另一個生物內。植入後，某些後果能夠得知，但大多是未知數；已知的基因工程的結果多為短期的、特定的和屬於物理方面的，未知的後果多屬於長期的、整體的和心態方面的。長期的效果也分特定（註4）和整體性的區別。
生物工程與人工繁殖的區分
人工繁殖動、植物，加快了大自然中本有的基因篩選和突變的過程，藉以挑選人類特定需求的品種。雖然挑選特定的品種，擾亂了自然界既有的篩選過程，但是所運用的是自然界中現有的方式。例如，繁殖馬匹只講求提升跑速，完全無視純種馬在野生環境中的存活率。在河流中人工養魚，導致原有的自然生態被排擠於外、而其本身缺乏免疫力、且將疾病傳染給野生魚等問題。（註5）
路德•博班（Luther Burbank）等人培育出各類美味新型水果；戴維斯加州大學培育出適合運輸包裝的硬皮方型番茄。培育的工作時而出錯，殺人蜂（killer bees）即是例證。另外，1973年的玉米枯萎病害，摧毀了三分之一的玉米作物；原因是新培育的玉米品種，極易受常見的葉（黴）微菌中，某類罕有變種菌的侵害。（註6）
生物工程師宣稱他們只是加快「物競天擇」的過程，並提高古老繁殖方式的效率。在某些個別情形下，這很可能是真的；但在多數情況下，這些生物工程師所設計的種種基因的改變，在自然界裡是絕對不會發生的，主要原因是他們所做的基因改變，僭越了物種之間的界限。
當前基因工程之應用
以下概述一些主要的新發展。（註7）
（一）目前基因工程的商業用途多屬於農業方面。通過基因工程改造的植物，能抵抗除草劑、殺蟲劑，並可直接在土壤中轉換氮。經由基因工程改造過的昆蟲，可直接攻擊作物害蟲。目前正在研究中的是，利用基因工程改造過的細菌，直接在實驗室裡培育農作物。同時在構想中領導市場新潮流的，是將基因工程改造過的植物，變為化工廠；目前通過這種方式生產的有機塑膠，即是一例。（註8）
（二）基因工程改造的動物，目前正被開發成為『活體工廠』，用於製造藥品，並提供人體器官移植的來源。（經由異種基因轉移的過程而創製的新動物，稱為「生命異種製版（xenographs）」；異種間器官移植，稱為「器官異種移植（xenotransplantation）」。基因工程與「生命複製（cloning）」相結合，帶動低脂肪食用動物等的研發，使魚類也藉此增大體型，加快成長速度。
附註：
3. 凡納迦•任普勒賽（Vanaja Ramprasad）所著、登載於一九九八年六月刊、第三十五冊〈生物科技與發展評論〉第二十四頁的「基因工程與養活全世界的神話」。
4. 舉例而言，特定的長期後果是某一品種的死亡或引發新的疾病生物體。
5. 一九九一年，加州登斯謬發生大規模殺蟲劑傾瀉事件後，在河中放養魚類（的作法）遇到強大的阻力，原因是會嚴重壓抑當地土產魚類的數量的回升。
6. 參考玟黛娜•施華（Vandana Shiva）所著，倫敦『禪圖書出版社』一九九三年出版的〈心田的單一耕作〉一書；以及波士頓『南端出版社』一九九七年出版的〈生物盜竊：自然與知識之掠奪〉第八十七至九十頁。將基因工程用之於農業，是單一耕作模式的一種極新式的延伸。亦參考下文有關所謂「終結者」基因的討論。
7. 此段落大部份依據傑瑞米•儒傅金（JeremyRifkin）所著、JP泰爾哲一九九八年出版的〈生物科技之世紀：駕馭基因改造世界〉第十五至三十二頁。
8. 見下文有關植物的次段落以及標題為「基因工程一些具體困難之處」的主段落。
待續 |
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...a gene is not an easily identifiable and tangible object. It is not only the DNA sequence which determines its functions in the organisms, but also its location in a specific chromosomal, cellular, physiological and evolutionary context. It is therefore difficult to predict the impact of genetic material transfer on the functioning of the extremely tightly controlled, integrated and balanced functioning of all the tens of thousands of structures and processes that make up the body of any complex organism.3 Genetic engineering refers to the artificial modification of the genetic code of a living organism. Genetic engineering changes the fundamental physical nature of the organism, sometimes in ways that would never occur in nature. Genes from one organism are inserted in another organism, most often across natural species boundaries. Some of the effects become known, but most do not. The effects of genetic engineering which we know are usually short-term, specific and physical. The effects we do not know are often long-term, general, and also mental. Long-term effects may be either specific4 or general.
DIFFERENCES BETWEEN BIOENGINEERING AND BREEDING
The breeding of animals and plants speeds up the natural processes of gene selection and mutation that occur in nature to select new species that have specific use to humans. Although the selecting of those species interferes with the natural selection process that would otherwise occur, the processes utilized are found in nature. For example, horses are bred to run fast without regard for how those thoroughbreds would be able to survive in the wild. There are problems with stocking streams with farmed fish because they tend to crowd out natural species, be less resistant to disease, and spread disease to wild fish.5
The breeding work of people like Luther Burbank led to the introduction of a whole range of tasty new fruits. At the University of California at Davis square tomatoes with tough skins were developed for better packing and shipping. Sometimes breeding goes awry. Killer bees are an example. Another example is the 1973 corn blight that killed a third of the crop that year. It was caused by a newly bred corn cultivar that was highly susceptible to a rare variant of a common leaf fungus.6
Bioengineers often claim that they are just speeding up the processes of natural selection and making the age-old practices of breeding more efficient. In some cases that may be true, but in most instances the gene changes that are engineered would never occur in nature, because they cross natural species barriers.
HOW GENETIC ENGINEERING IS CURRENTLY USED
Here is a brief summary of some of the more important, recent developments in genetic engineering.7
1) Most of the genetic engineering now being used commercially is in the agricultural sector. Plants are genetically engineered to be resistant to herbicides, to have built in pesticide resistance, and to convert nitrogen directly from the soil. Insects are being genetically engineered to attack crop predators. Research is ongoing in growing agricultural products directly in the laboratory using genetically engineered bacteria. Also envisioned is a major commercial role for genetically engineered plants as chemical factories. For example, organic plastics are already being produced in this manner.8
2) Genetically engineered animals are being developed as living factories for the production of pharmaceuticals and as sources of organs for transplantation into humans. (New animals created through the process of cross-species gene transfer are called xenographs. The transplanting of organs across species is called xenotransplantation.) A combination of genetic engineering and cloning is leading to the development of animals for meat with less fat, etc. Fish are being genetically engineered to grow larger and more rapidly.
NOTES:
3. Vanaja Ramprasad. "Genetic engineering and the myth of feeding the world." Biotechnology and Development Monitor No. 35 (June, 1998): 24.
4. Examples of specific long term effects are the death of a particular species or the introduction of a new disease organism.
5. After a major pesticide spill in Dunsmuir, California, in 1991, there was much opposition to stocking the river because it would strongly discourage the revival of the native fish populations.
6. See Vandana Shiva, Monocultures of the Mind (London: Zen books, 1993) and Biopiracy: the Plunder of Nature and Knowledge (Boston: South End Press, 1997), pp. 87-90. The use of genetic engineering in agriculture is a radical new extension of the monoculture paradigm. See also the discussion of the so-called 'Terminator" genes below.
7. Most of this section is based on Jeremy Rifkin, Biotech Century: Harnessing the Gene and Remaking the World (J. P. Tarcher, 1998), pp. 15-32.
8. See below in the subsection on plants the section entitled "Some Specific Difficulties with Genetic Engineering."
To be continued |
