职称英语综合类阅读理解英文及译文克隆农场

　　克隆农场

　　工业化农场很快会进入一个大产量的新领域。美国的公司正在开发一项需要大规模克隆小鸡的技术。一旦一个具有所期望特性的小鸡被孵化出来或被基因改造，每小时成千上万的鸡蛋会孵出如出一辙的小鸡滚下生产线。每年上百万的克隆小鸡能被孵化出来，从而为鸡场提供以相同比例生长，重量相同并且味道相同的小鸡。

　　这至少是美国国家科技院的梦想，科技院给OnrigenTherapeuticsofBurlinggame,California，以及EmbrexofNorthCaroling470万基金以资助研究。这个预想为担忧增加鸡场小鸡痛苦的动物福利组织拉响了警报。

　　那好像并没有让使家禽养殖业气馁，然而，他们想使抗痛小鸡吃得更少，长得更快，养殖者希望减少投入但仍获得相同的产量，MikeFitzgeraldofOrigen说，为了达到这个要求，Origen致力于制造一个有效克隆体的小鸡，他说，正常的克隆技术对鸟类无效，因为卵不能被移动或移植。然而，公司正试图大量繁殖刚产下的受精卵中提取的胚胎的干细胞。技巧是在细胞开始显示其差别前对其进行培育，这样它们还保持多能性。Fitzgerald说。

　　运用早已形成的技术，这些干细胞会被注入刚孵出的，已受精的，要接受细胞植入的鸡蛋的胚胎中，形成一个嵌合体的小鸡。严格地说，嵌合体的小鸡不是克隆鸡，因为它既有植入的细胞又有本身的细胞。但Fitzgerald说，如果小鸡身体的95%是由被植入的细胞发展而来的就足够了。在家禽界，不是100%也没关系。

　　Origen面临的另一个挑战是提高生产量。为了做到这点，他和Embrex合作研制了一个可将疫苗注入50000个鸡蛋中的仪器。Embrex正试图改造那个仪器，从而使胚胎和注射的细胞落在准确的位置而不杀死它。

　　在将来，Origen设想将不同品种小鸡的干细胞冷冻，如果定单要某一种小鸡，成百万的卵能在几个月甚至几个星期被生产出来，目前，维持市场可能需要的各种小鸡对养殖者来说太昂贵了，那要花数年的时间培育足够多的小鸡以生产出农民需要的上百万鸡蛋。

　　Clone Farm

　　Factory farming could soon enter a new era of mass production. Companies in the US are developing the technology needed to clone chickens on a massive scale. Once a chicken with desirable traits has been bred or genetically engineered, tens of thousands of eggs, which will hatch into identical copies, could roll off the production lines every hour. Billions of clones could be produced each year to supply chicken farms with birds that all grow at the same rate, have the same amount of meat and taste the same.

　　This, at least, is the vision of the USs National Institute of Science and Technology, which has given Origen Therapeutics of Burlingame, California, and Embrex of North Carolina $4.7 million to help fund research. The prospect has alarmed animal welfare groups, who fear it could increase the suffering of farm birds.

　　Thats unlikely to put off the poultry industry, however, which wants disease resistant birds that grow faster on less food. Producers would like the same meat quantity but to use reduced inputs to get there, says Mike Fitzgerald of Origen. To meet this demand, Origen aims to create an animal that is effectively a clone, he says. Normal cloning doesnt work in birds because eggs cant be removed and implanted, Instead, the company is trying to bulk-grow embryonic stem cells taken from fertilized eggs as soon as theyre laid. The trick is to culture the cells without them starting to distinguish, so they remain pluripotent, says Fitzgerald.

　　Using a long-established technique, these donor cells will then be injected into the embryo of a freshly laid, fertilized recipient egg, forming a chick that is a chimera. Strictly speaking a chimera isnt a clone, because it contains cells from both donor and recipient. But Fitzgerald says it will be enough if, say, 95 percent of a chickens body develops from donor cells. In the poultry world, it doesnt matter if its not 100 percent, he says.

　　Another challenge for Origen is to scale up production. To do this, it has teamed up with Embrex, which produces machines that can inject vaccines into up to 50,000 eggs an hour. Embrex is now trying to modify the machines to locate the embryo and inject the cells into precisely the right spot without killing it.

　　In future, Origen imagines freezing stem cells from different strains of chicken. If orders come in for a particular strain, millions of eggs could be produced in months or even weeks. At present, maintaining all the varieties the market might call for is too expensive for breeders, and it takes years to bread enough chickens to produce the billions of eggs that farmers need.