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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  48
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.
The word "taxing" (Line Para. 5) is closest in meaning to
选项 A、straightforward.
B、impossible.
C、demanding.
D、inherent.
答案C
解析 语义理解题。第五段第四句说，除了要求低错误率，x基金会还要求序列的完整性——排序结果必须包括98％以上的碱基对。然后第五句说这个要求比较taxing，接着交代了原因，因为染色体的某些部分很难获得，可见taxing与not easy语义相近，即这个要求比较难实现。所以[C]是答案。更大的成果，即对如何健康地步入晚年的了解，以及对医学科学的推动，将最终惠及每个人。
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