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  3. In Britain, those who live to be 100 years old receive a birthday card from the queen. In the future, centenarians everywhere ma

In Britain, those who live to be 100 years old receive a birthday card from the queen. In the future, centenarians everywhere ma

admin2015-07-27  39
问题     In Britain, those who live to be 100 years old receive a birthday card from the queen. In the future, centenarians everywhere may also receive a call from a geneticist. If they do, he or she will be seeking a sample of DNA that might, eventually, help to reveal the genetic components of extreme longevity. The more immediate use, however, will be in a competition. For on October 26th the X Prize Foundation, based in Playa Vista, California, unveiled its latest carrot to the world’s scientists.
    The foundation has already put up prizes in areas as diverse as cleaning up oil spills and landing a robot on the moon. The idea of a genomics X prize is not new. It has been around since 2006. But the latest announcement, in the pages of Nature Genetics, has a particular goal in mind.
    The foundation is offering $10m to the first team to sequence the genomes of 100 centenarians. The winners will have to do it accurately, making no more than one mistake per million base pairs (the chemical letters in which genomic information is encoded). They will have to do it cheaply, spending less than $1,000 per genome. And they will have to do it quickly, within 30 days of starting.
    The goal of the project is twofold. First, to discover what, genetically speaking, makes centenarians different from other people. And second, to try to establish an industry standard for sequencing. This is something the field sorely needs. The cost of sequencing has plummeted over the past decade, and several technologies have emerged, each backed by different firms which will, for a suitable consideration, happily sequence your genome. No two firms, however, are likely to produce the same result. The full genome has 6 billion base pairs (3 billion from each parent, though many are duplicates), which means even the prize winner will be allowed 6,000 mistakes. And some parts, particularly those where the same short pattern of base pairs is repeated over and over again, remain difficult to sequence well. Moreover, several techniques are inherently unreliable, having traded speed and simplicity for accuracy.
    The new X prize is designed to winnow the genetic wheat from the chaff. The scientific standards for victory have been set by a team led by Larry Kedes. Dr. Kedes, who founded the Institute for Genetic Medicine at the University of Southern California, is the foundation’s main adviser on matters genomic. Besides the low error rate, Dr. Kedes requires that the sequence be complete-meaning that it includes at least 98% of the genome’s base pairs. That is taxing because some parts of a chromosome, such as those near the centromere (the place where the two arms of a chromosome meet) are not easy to get at. He also requires that it be sorted by haplotype. A haplotype is a group of genes that tend to travel through the generations as a block. Dr. Kedes wants it to be clear which haplotypes came from which parent.
    The contest will begin in January 2013 and last 30 days. The first team to score their century of genomes — at the new standards, price and speed — will win the prize. But the wider prize, an understanding of how to stay healthy into a ripe old age, with all that may bring to medical science, will ultimately be shared by everybody.
There can’t be identical sequencing results for the same individual because
选项 A、different companies use different technologies.
B、there remain some technical difficulties.
C、it is impossible to duplicate all the genomes.
D、technicians are not careful enough seeking speed.
答案B
解析 事实细节题。第四段第六句说，没有两家公司的测序结果相同的可能，后面对这种现象作出解释。第七句大意说，基因组数目庞大，排序中出现误差不可避免。第八句说，那些短型碱基对被不断复制的位置，仍然很难准确测序。第九句说，好几种测序技术本身就不可靠。总结一下，就是在技术上实现完全准确还有难度，[B]为答案。虽然有很多公司提供基因排序服务，但并没有说他们使用完全不同的技术，排除[A]。duplicates在本段中的意思是很多碱基对被不断复制，[C]曲解原文，排除。[D]是对第四段最后一句提到的有些排序技术不可靠的过度推断，技术有问题而不是technicians不认真。
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