转基因作物的潜在生态风险
　　转基因作物因为是人工制造的品种，我们可以把这些品种看作为自然界原来不存在的外来种。一般说来，外来种对环境或生物多样性造成威胁或危险会有一段较长的时间。有时需10年的时间，或更长的时间。转基因作物商品化种植至今最长也就是5～6年的时间，一些潜在风险在这么短的时间内不一定能表现出来。可是有些风险在实验室水平上已经证实。如Mikkelsen等证实抗除草剂转基因油菜的抗除草剂基因可以通过基因流在一次杂交、一次回交的过程已转到其野生近缘种中（Mikkelsen et al., 1996）。
对环境有害的影响
　　农田生态系统Agro-ecosystem
　　增加杀虫剂的使用——抗性的选择和转运到可相容的其它植物中
　　产生新的农田杂草——基因流和杂交
　　转基因植物自身变为杂草——插入性状的竞争
　　产生新的病毒——不同病毒基因组和转基因作物的病毒外壳蛋白的重组
　　产生新的作物害虫

本文发表在 rolia.net 枫下论坛A genetically modified organism (GMO) or genetically engineered organism (GEO) are organisms whose genetic material has been altered using genetic engineering techniques. These techniques, generally known as recombinant DNA technology, use DNA molecules from different sources, which are combined into one molecule to create a new set of genes. This DNA is then transferred into an organism, giving it modified or novel genes. Transgenic organisms, a subset of GMOs, are organisms which have inserted DNA that originated in a different species.

Bacteria were the first organisms to be modified in the laboratory, due to their simple genetics. These organisms are now used for several purposes, and are particularly important in producing large amounts of pure human proteins for use in medicine. Genetically modified bacteria are used to produce the protein insulin to treat diabetes. Similar bacteria have been used to produce clotting factors to treat hemophilia, and human growth hormone to treat various forms of dwarfism.

Transgenic animals are used as experimental models to perform phenotypic and for testing in biomedical research. Genetically modified animals are becoming more vital to the discovery and development of cures and treatments for many serious diseases. By altering the DNA or transferring DNA to an animal, we can develop certain proteins that may be used in medical treatment. Stable expressions of human proteins have been developed in many animals, including sheep, pigs, and rats.

However there have been no such disadvantages of genetically modified organisms proved on a scientific point of view. But there are always ethical protests placed on them. Firstly it’s said that genetically modified results in formation of transgenic plants and animals. So there may be a chance of loss of genetic diversity upon wide use of this process on particular species, if care is not taken to preserve genetic material of the original organisms.


Also artificial genetic modifications of a desired organism may result in simultaneous natural genetic or other modifications of an undesired organism. For example, on modifying a plant to be resistant to a particular disease-causing organism, the latter may acquire natural variations which may enable it to infect other plant species not previously infected. Furthermore some people complain that by modifying different agricultural plants to increase quantity, resistance etc. The natural taste of the food product somehow gets disrupted. However there is no scientific evidence to support these disadvantages.更多精彩文章及讨论，请光临枫下论坛 rolia.net

本文发表在 rolia.net 枫下论坛One benefit of cloning human tissue is that if we can grow vital organs, they can be used to replace ailing organs. For example, if heart disease destroys a patient's heart, an exact replica can simply be "grown" to replace it.
There are several advantages to the cloning of animals and to the cloning of human cells. Along with each of the advantages, however, there are disadvantages, risks, and warnings.

There are five important reasons why animal cloning might be useful: (1) to generate groups of genetically identical animals for research purposes; (2) to rapidly propagate desirable animal stocks; (3) to improve the efficiency of generating and propagating transgenic livestock; (4) to produce targeted genetic alterations in domestic animals; (5) to pursue basic knowledge about cell differentiation.

Cloning animals for research purposes is attractive to many scientists, because the experimental variation that often occurs with genetic differences is eliminated. This process is limited in its usefulness, however, because keeping a homozygous line is going to be difficult. Also, the overall process promises to be expensive for most animals.

Having a speedy method to breed favorable livestock has great commercial importance. Nuclear transfer may be the wave of the future to rapidly produce desirable stocks of animals. The ultimate consequences could be dangerous, however, because genetic diversity could be eliminated. Strict regulation of cloning would ensure that this would not happen, though.

The improved generation and propagation of transgenic livestock becomes of interest to the pharmaceutical and medical world. Genetically altering farm animals by the introduction and expression of genes from other species proves to be a useful technology for the future. For example, the milk of livestock animals can be modified to contain large amounts of pharmaceutically important proteins such as insulin or factor VIII for treatment of human disease by expressing human genes in the mammary gland. Also, transgenic animals could become useful for organ transplantation into humans.

Generating targeted gene alterations in domestic animals can be helpful in studying mutations of genes in a very controlled manner. Gene targeting approaches can also be used to ensure correct tissue-specific expression of foreign genes and to suppress the expression of genes in inappropriate tissues. It could also be used to directly alter normal genes, which could influence animal health and productivity.

Basic research on cell differentiation has come about with the arrival of Dolly. Developmental biologists will want to know which genes are reprogrammed, when they are expressed, and in what order. This may or may not shed some light on the specialization that occurs during the development of therapies to treat human disease.

The agricultural industry could reek the benefits of this new technology by having the ability to produce multiple identical copies of a cow that produces a lot of mile, a sheep that produces a lot of wool, and so on. They could create an elite stock of farm animals.

The most exciting prospect here is to modify a sheep CTFR gene to create a model of cystic fibrosis (CF) for gene therapy. In a classy move, Ian Wilmut sold the first wool shorn from Dolly to raise money for the care and treatment of kids with CF.

There are five potential uses for cloning humans or human cells: (1) a research tool to understand how genes in cells can be switched off and on; (2) growing new skin for burn victims; (3) culturing bone marrow that could be used to treat cancer patients; (4) manipulating genes to cure sickle cell anemia; (5) potential application in treating infertility.

A more controversial benefit is to provide children for lesbian couples. Normally they need an outsider to donate sperm; with cloning they would be able to avoid this.

There are several disadvantages associated with cloning, such as significant scientific uncertainty, medical risks, potential effects of aging, somatic mutation, and improper imprinting. A cloned child is not really a couple’s genetic child, but the child of only one of them. That imbalance may produce strains on the marriage the child might suffer identity confusion, and there is a risk of perpetuating the cause of sterility.

besides......
Human cloning can also be a solution for infertile couples, even allowing the couples to create a child with certain features. Because cloning allows for the manipulation of genes, embryos can be created free of inherited genetic disorders or predispositions.
The cloning of human tissue could also be used to treat cancers, and even for plastic surgery.更多精彩文章及讨论，请光临枫下论坛 rolia.net

本文发表在 rolia.net 枫下论坛(1) 以前, 我想当然, 杂交水稻肯定是不同水稻之间的授粉, 即夫系, 母系都是水稻, 如果是这样的水稻, 是不是不需要做任何实验就可以认为是安全的?

首先先给安全下个定义。不仅仅是定性的，而且需要定量的，这才有意义。自从转基因植物诞生前，好像没有任何一类人士或组织对染色体水平的杂交品种提出过生物安全性问题。您这个问题，其实送给袁隆平最合适。


(2) 现在感觉杂交育种, 夫系, 母系一方是本系植物, 另一方有可能是其它植物, 我的理解对吗? 如果这样, 这类种子的安全吗? 是否需要做实验?

在转基因植物中，基因的来源植物与目标植物可以是不同的物种。但是，亲缘关系越近的物种，基因成功转入并表达的概率越高。美国，中国以及很多国家都对转基因作物获得批准，设立了严格的检测和审批程序。但还没听说对传统方法（染色体水平）育出的作物品种进行生物安全性检测的法规。


(3)袁教授并没有谈到转基因棉花, 是您为了科普有意介绍给大家的吗? 您所说的人体内的蛋白酶是否永远都保持一定的数量? 有没有可能有其它因素会影响此蛋白酶的数量? 例如毒奶粉成年人喝喝,不会出事, 因为成年人还会喝水, 但婴儿喝, 风险就明显增大很多.

是的，“毒蛋白”是一个严重以讹传讹的故事，值得正视听。生物体内的各种酶，都会在不同的生理状态下发生变化。比如说，你发烧了，你的体温
超过了酶的最适合的反应温度，酶的活性会降低，这时候，你再多吃高脂肪，高蛋白的食物，就不容易消化了。所以，发烧的时候人的消化功能是会降低的。

毒奶粉则是另外一个故事：其中的三聚氰胺是非蛋白含氮化合物。不良商家将其加入奶粉中，是因为奶粉的蛋白质测定方法决定的。现行的奶粉标准中，蛋白质含量是一项重要的指标。蛋白质是一类含氮的生物大分子，测定奶粉中的蛋白质含量，是先测量奶粉中含氮量，之后用一个系数折算成蛋白质的含量。不良商家为了以低蛋白品充当高蛋白品，就加入便宜的三聚氰胺这个非蛋白的含氮化合物。这样一来，奶粉测量出的含氮量很高，但据之折算出的蛋白质含量则大含水分了。说到毒性，其实三聚氰胺的毒性并不大，我忘了它的级别。但是，这些含氮化合物是经人的肾脏代谢掉的。成年人代谢能力相对于幼儿为强，所以，如果不是长期大量服用，则问题不太大。对于幼儿，由于肾脏发育尚不完善，功能也较成年人弱很多，其代谢能力有限，摄入无用的非蛋白含氮物质，会加重肾脏的负担，长期以往，会对幼儿肾脏造成损伤。


(4) 转基因种子的安全性完全基于您那句话:"科学家不知做了多少安全性的验证". 但一个东西与金钱靠上, 是否能做到真正的公正? 例如麦当劳最近才宣布"粉红泥"事件. 另外, 科学家是否所有极端情况都考虑到了? "智者千虑,必有一失"?


所有，极端，这些词真的不是属于科学范畴了。天下所有的公正只有相对的，没有绝对的，这是一个逻辑命题。


(5) "有人说，世界上最可怕的是人。为啥这么说呢，就是因为见过成万上千的人, 知道人性的弱点和人性的丑陋。人们的恐惧，来自于对人类本身的了解."

智者见智吧，我就不怕人，啥人都不怕。


最后, 再次表示感谢. 从现在起, 我知道杂交种子也可能不安全更多精彩文章及讨论，请光临枫下论坛 rolia.net