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  3. Several research groups in the United States are conducting genetic research aimed at retarding aging. If the breakthroughs of r

Several research groups in the United States are conducting genetic research aimed at retarding aging. If the breakthroughs of r

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问题     Several research groups in the United States are conducting genetic research aimed at retarding aging. If the breakthroughs of recent years are anything to go by, it is likely that we will see several-fold longevity increases in mice within the next decade or so. Already such genetic manipulation has increased by almost 50% the life span of flies. Results are also promising in mammals: scientists have extended longevity in mice by 50% through genetic interventions. Achieving similar results in humans will be harder. Scientists have already identified genes that appear to accelerate human aging, but they have yet to find genes with the opposite effect. But with the sequencing of the human genome, we are now in a better position to find out more about aging in humans as well as animals.
    For those who cannot wait, there is one method available today that might delay human aging, caloric restriction. This means simply a diet with few calories. Experiments have shown longevity increases of more than 50% in certain mammals that follow such diets. Most people, however, feel that the secondary effects of this outweigh the benefits. After all, what is the point of living longer if you cannot enjoy life? If science is to extend human longevity, it will have to do so by extending the duration of human life in age-related disability. The extra years of life must allow future grandparents to enjoy life, not just live.
    Although some scientists argue that aging will never be cured and our grandparents will continue to fit our stereotypes, many others remain confident that we will soon learn how to modulate the human aging process. " I believe our generation is the first to be able to map a possible route to individual immortality," says William Haseltine, CEO of Human Genome Sciences Inc. in Rockville, Maryland. If a therapy could slow human aging by 50% , for instance, we could have 30 or 40 more years of life. In that time, new discoveries could be made that would allow us to live even longer, and the cycle could continue until a cure for aging is discovered. "It’s possible that some people a-live now may still be alive 400 years from now," claims gerontologist S. Michal Jazwinski of Louisiana State of University Health Sciences Center. But what would be consequences of extending human longevity or finding a real cure for aging?
    Researchers have achieved success in【A1】______the aging of flies. But similar results in humans are not encouraging. Other than finding genes that slow down human aging, scientists have identified genes that appear to【A2】______it. However, there might be one way of delaying aging, i. e. caloric【A3】______which means following certain diets with few calories. Meanwhile, it is necessary to think about the significance of living longer and how to【A4】______the aging process. Some optimistic people believe that it is possible to extend human longevity while others are quite concerned about the【A5】______of it.
【A3】
选项
答案restriction
解析 (第二段第一句提到有一种方法可以延缓衰老，那就是caloric restriction。)
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C类竞赛（非英语专业本科）

大学生英语竞赛（NECCS）

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