Irma

托福閱讀 練習小短文 - P53腫瘤蛋白(醫學學科) 

這是一篇有關腫瘤抑制蛋白的研究報告，裡面包含基因相關內容，其實多年來非常多的學者在研究如何抑制癌症與發生的原因，因此像這類的相關研究報告和新聞都是非常多的，托福在生物或醫學學科裡面非常愛提到細胞相關的研究內容，所以這類相關的單字要盡可能多看多熟悉。

Why elephants aren’t riddled with tumors poses a weighty problem for researchers. A new study shows that the animals harbor dozens of extra copies of one of the most powerful cancer-preventing genes. These bonus genes might enable elephants to weed out potentially cancerous cells before they can grow into tumors.

When it comes to cancer, elephants appear to have several strikes against them. At up to 4800 kg, an African elephant packs about 100 times as many cells as you do. The more cells an animal carries, the higher the odds that one of them will suffer the DNA damage that can lead to cancer. Producing all those cells also entails numerous rounds of cell division, each of which can result in a tumor-triggering DNA break. Moreover, elephants can survive for more than 60 years in the wild, providing plenty of time for tumors to arise. “Long-lived animals with lots of cells should all be dropping dead of cancer,” says pediatric oncologist Joshua Schiffman of the University of Utah’s Huntsman Cancer Institute in Salt Lake City, who is a co-author on the new study. “But they don’t or they’d go extinct.”

The surprisingly low cancer rates in elephants and other hefty, long-lived animals such as whales—known as Peto’s paradox after one of the scientists who first described it—have nettled scientists since the mid-1970s. So far, researchers have made little progress in solving the mystery or determining how other long-lived species beat cancer. One exception involves naked mole rats. Although these African rodents aren’t massive, they survive for up to 28 years, almost 10 times longer than lab rats, and they don’t develop cancer. Two years ago, cell and molecular biologists Vera Gorbunova and Andrei Seluanov of the University of Rochester in New York and colleagues reported that one of naked mole rats’ defenses against cancer was a complex sugar called hyaluronan, which prevents their cells from clumping together to form tumors.