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(单词翻译:双击或拖选)

This is Scientific American’s 60-Second Science. I’m Cynthia Graber. This will just take a minute.

Saliva¹ contains many useful components²: lubricants, enzymes³ for breaking down food and now compounds that can reveal a person’s age. That’s according to a study in the journal Public Library of Science ONE.

During normal development, DNA⁴ in your body gets what’s called methylated. Small chemicals called methyl groups bind⁵ to the DNA, helping⁶ to determine which genes⁷ become active. But the patterns of methylation change as we grow older, which was a clue that measuring methylation might give away age.

The researchers studied DNA in saliva contributed by 34 pairs of male identical twins, ages 21 to 55. They found 88 sites on the men’s DNA where the amount of methylation correlated with their ages. The scientists next verified that finding in 60 men and women, ages 18 to 70.

Then they narrowed in on two genes that had the strongest age-related correlation⁸. And using just that data, they found that they could estimate the ages of their saliva contributors to within five years.

This technique might help in crime scene investigations—recovered saliva could tell the age of a perpetrator. So if you’re worried about anyone knowing how old you are, be careful where you spit.

Thanks for the minute. For Scientific American’s 60-Second Science, I’m Cynthia Graber.

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收听单词发音

1 saliva
n.唾液，口水
参考例句：
He wiped a dribble of saliva from his chin.他擦掉了下巴上的几滴口水。 Saliva dribbled from the baby's mouth.唾液从婴儿的嘴里流了出来。

2 components
（机器、设备等的）构成要素，零件，成分；成分( component的名词复数 )； [物理化学]组分； [数学]分量；（混合物的）组成部分
参考例句：
the components of a machine 机器部件 Our chemistry teacher often reduces a compound to its components in lab. 在实验室中化学老师常把化合物分解为各种成分。

3 enzymes
n. 酶，酵素
参考例句：
It was said that washing powders containing enzymes remove stains more efficiently. 据说加酶洗衣粉除污更有效。 Among the enzymes which are particularly effective are pepsin, papain. 在酶当中特别有效的是胃朊酶、木瓜酶。

4 DNA
(缩)deoxyribonucleic acid 脱氧核糖核酸
参考例句：
DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。 Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。

5 bind
vt.捆，包扎；装订；约束；使凝固；vi.变硬
参考例句：
I will let the waiter bind up the parcel for you.我让服务生帮你把包裹包起来。 He wants a shirt that does not bind him.他要一件不使他觉得过紧的衬衫。

6 helping
n.食物的一份&adj.帮助人的，辅助的
参考例句：
The poor children regularly pony up for a second helping of my hamburger. 那些可怜的孩子们总是要求我把我的汉堡包再给他们一份。 By doing this, they may at times be helping to restore competition. 这样一来, 他在某些时候,有助于竞争的加强。

7 genes
n.基因( gene的名词复数 )
参考例句：
You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。来自《简明英汉词典》 Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。来自英汉非文学 - 生命科学 - 生物技术的世纪

8 correlation
n.相互关系，相关，关连
参考例句：
The second group of measurements had a high correlation with the first.第二组测量数据与第一组高度相关。 A high correlation exists in America between education and economic position.教育和经济地位在美国有极密切的关系。