题型:阅读理解 题类:常考题 难易度:普通
河南省林州市第一中学2019-2020学年高二上学期英语9月月考试卷
Why elephants rarely get cancer is a mystery that has confused scientists for decades. A study was led by researchers at Huntsman Cancer Institute (HCI) at the University of Utah and Arizona State University, including researchers from the Ringling Bros. Center for Elephant Conservation may have found the answer. According to the results, elephants have 38 additional modified copies of a gene (基因) that encodes p53, a well-defined tumor (肿瘤) suppressor, as compared to humans, who have only two. Further, elephants may have a more powerful mechanism for killing damaged cells that are at risk for becoming cancerous. In isolated elephant cells, this activity is doubled compared to healthy human cells, and five times that of cells from patients with Li-Fraumeni Syndrome, who have only one working copy of p53 and more than a 90 percent lifetime cancer risk in children and adults. The results suggest extra p53 could explain elephants' increased resistance to cancer.
"Nature has already figured out how to prevent cancer. It's up to us to learn how different animals overcome the problem so we can adapt those strategies to prevent cancer in people," says co-senior author Joshua Schiffman, M.D., pediatric oncologist (肿瘤学家) at Huntsman Cancer Institute, University of Utah School of Medicine, and Primary Children's Hospital.
According to Schiffman, elephants have long been considered a walking problem. Because they have 100 times as many cells as people, they should be 100 times more likely to have a cell slip into a cancerous state and cause the disease over their long life span of 50 to 70 years. And yet it's believed that elephants get cancer less often, a theory confirmed in this study. Analysis of a large database of elephant deaths estimates a cancer death rate of less than 5 percent compared to 11 to 25 percent in people.
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