介绍： This is Scientific American's 60-second Science, I'm Eliene Augenbraun.
How old is your four-legged best friend? Common wisdom says that a dog ages seven years for every human year. But Tina Wang, a graduate student at the University of California, San Diego, wanted a more accurate assessment. Her quest start...

介绍： This is Scientific American's 60-second Science, I'm Eliene Augenbraun.
How old is your four-legged best friend? Common wisdom says that a dog ages seven years for every human year. But Tina Wang, a graduate student at the University of California, San Diego, wanted a more accurate assessment. Her quest started five years ago, when she rescued a dog from a shelter.
"I kind of just wanted to ask how old she was cause I felt like they were giving me an age that was very sensible, but I wasn't sure she was actually that old. So that kind of started this whole project."
Wang worked in Trey Ideker's lab, where they study changing patterns of DNA methylation in humans. Small chemical entities called methyl groups attach to stretches of DNA, which affects what sequences are active. As we age, some stretches of DNA get more methylated, and others less. The pattern is so consistent over the course of most people's lives that it can be used as an aging "clock."

这里是科学美国人――60秒科学系列，我是艾琳·奥根布劳恩。
你的四条腿最好朋友多大了？普遍认为，狗狗1岁相当于人类7岁。但加州大学圣地亚哥分校的研究生蒂娜·王希望得到更准确地评估狗狗年龄。她的探索始于五年前，当时她从收容所救出了一只狗。
“我想问这只狗多大了，因为他们告诉了我一个合乎情理的年龄，但我并不确定它是否真的那么大。由此开启了整个项目。”
王在特雷·艾德克的实验室工作，他们在那里研究人类DNA甲基化模式的变化。被称为“甲基原子团”的小化学实体附着在DNA片段上，这会对哪些序列是活跃的产生影响。随着年龄的增长，一些DNA片段的甲基化程度会上升，而另一些则会下降。在大多数人的生命中，这种模式是如此的一致，以至于它可以被看作老化“时钟”。