By analyzing the DNA of the world's oldest people, Boston University scientists said Thursday they have discovered a genetic signature of longevity. They expect soon to offer a test that could let people learn whether they have the constitution to live to a very old age.

The researchers, who studied more than 1,000 people over the age of 100, identified a set of 150 unique genetic markers that, taken together, are linked to extreme longevity. They acknowledged they didn't know all the genes involved, nor their exact function in extending old age.

'This is an extremely complex trait that involves many processes,' said lead researcher Paola Sebastiani, a biostatistician at BU's School of Public Health. Even so, 'we can compute your specific predisposition to exceptional longevity.'

The researchers said they had no plans to patent the technique or profit from it. Instead, they expect to make a free test kit available on the Internet later this month to foster longevity research.

The test might reveal more than some people would like to know, the BU scientists warned. Genetic testing often reveals tantalizing but incomplete information, and it is sometimes difficult to know how to respond. People with genes for extreme longevity could face a series of difficult decisions about their careers, retirement savings, insurance coverage, medical treatments and marriages in old age.

'I don't think people are ready for this from a social point of view,' said BU geriatrician Thomas Perls, the other lead researcher. 'But I don't think that will stop companies from trying to market this.'

Scientists have long sought to crack the genetic code of healthy aging. On average, people in developed countries can expect to live between 80 and 85 years, largely as a result of improvements in diet and public health. But the oldest of the old -- the 'wellderly' -- live two to three decades longer, often free of mental and physical ailments.

The oldest person alive today is 116 years old, according to the Los Angeles Gerontology Group. The oldest person on record lived to be 122.

No one knows the complete prescription for a healthy long life. But genes that help control cellular responses to famine, drought and other survival stresses may play a key role in staving off the diseases and chronic ailments of aging, research suggests.

The free test will be available through a public website maintained by the New England Centenarian Study. But to take the test, people will have to provide their own complete genome -- which currently can cost thousands of dollars from gene-sequencing companies.

Robert Lee Hotz

• constitution [,kɔnsti´tju:ʃən] n.宪法；体格；体质 (初中英语单词)
• extreme [ik´stri:m] a.尽头的 n.极端 (初中英语单词)
• function [´fʌŋkʃən] n.机能；职责 vi.活动 (初中英语单词)
• extremely [ik´stri:mli] ad.极端地；非常地 (初中英语单词)
• complex [´kɔmpleks] a.复杂的 n.综合企业 (初中英语单词)
• patent [´peitənt, ´pæ-] a.专利的 n.专利品 (初中英语单词)
• available [ə´veiləbəl] a.可用的；有效的 (初中英语单词)
• respond [ri´spɔnd] v.回答；响应；有反应 (初中英语单词)
• series [´siəri:z] n.连续；系列；丛书 (初中英语单词)
• medical [´medikəl] a.医学的；医疗的 (初中英语单词)
• healthy [´helθi] a.健康的 (初中英语单词)
• mental [´mentl] a.精神的；心理的 (初中英语单词)
• physical [´fizikəl] a.物质的；有形的 (初中英语单词)
• research [ri´sə:tʃ] n.&vi.调查；探究；研究 (初中英语单词)
• signature [´signətʃə] n.签名；盖章 (高中英语单词)
• studied [´stʌdid] a.故意的；有计划的 (高中英语单词)
• unique [ju:´ni:k] a.唯一的 n.独一无二 (高中英语单词)
• specific [spi´sifik] a.具体的；特有的 (高中英语单词)
• foster [´fɔstə] vt.促进；推动；鼓励 (高中英语单词)
• famine [´fæmin] n.饥荒 (高中英语单词)
• compute [kəm´pju:t] v.&n.计算；估计 (英语四级单词)
• exceptional [ik´sepʃənəl] a.异常的，特别的 (英语四级单词)
• retirement [ri´taiəmənt] n.退休；撤退；幽静处 (英语四级单词)
• trying [´traiiŋ] a.难堪的；费劲的 (英语四级单词)
• drought [draut] n.旱灾；干旱 (英语四级单词)
• technique [tek´ni:k] n.技术；技巧；方法 (英语六级单词)
• incomplete [,inkəm´pli:t] a.不完全的，未完成的 (英语六级单词)
• chronic [´krɔnik] a.慢性的；剧烈的 (英语六级单词)