60秒科学:Genome: Now in 3-D!

Genome: Now in 3-D!
In a study in the journal Science, researchers report the mapping of the three-dimensional structure of the human genome, and the finding that the cell's nucleus¹ is divided into two regions, one where DNA² goes to get expressed. Cynthia Graber reports

If the human genome were put in a straight line, it would be over six and a half feet long. So how do you store all that DNA in a tiny nucleus? And have the cell manage it? Researchers explain how in a study featured on the cover of the October 9th issue of the journal Science.

Using new analytic³ techniques, Erez Lieberman and colleagues found that the genome is packed into what’s called a “fractal globule”—despite being intensely twisted, the string of genes⁴ never knots. This type of shape was mathematically postulated⁵ over a century ago, and has now been shown to describe the genome’s three-dimensional structure.

But the big finding is that the cell nucleus has two compartments—and genes are only active in one. All cells carry the same complete genome, but different genes get turned on, for example, in a liver cell compared with a nerve cell. Turns out that the genes to be used in a given cell get shuttled into the nucleus’s active section. Dormant⁶ genes stay out. The system allows each cell to make sense of information stored trillions of times more densely⁷ than what’s on a computer chip.

—Cynthia Graber
 

1 nucleus   

n.核，核心，原子核

参考例句：

• These young people formed the nucleus of the club.这些年轻人成了俱乐部的核心。
• These councils would form the nucleus of a future regime.这些委员会将成为一个未来政权的核心。

2 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。

3 analytic   

adj.分析的，用分析方法的

参考例句：

• The boy has an analytic mind. 这男孩有分析的头脑。
• Latin is a synthetic language,while English is analytic.拉丁文是一种综合性语言，而英语是一种分析性语言。

4 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

5 postulated   

v.假定，假设( postulate的过去式和过去分词 )

参考例句：

• They postulated a 500-year lifespan for a plastic container. 他们假定塑料容器的寿命为500年。
• Freud postulated that we all have a death instinct as well as a life instinct. 弗洛伊德曾假定我们所有人都有生存本能和死亡本能。 来自辞典例句

6 dormant   

adj.暂停活动的；休眠的；潜伏的

参考例句：

• Many animals are in a dormant state during winter.在冬天许多动物都处于睡眠状态。
• This dormant volcano suddenly fired up.这座休眠火山突然爆发了。

7 densely   

ad.密集地；浓厚地

参考例句：

• A grove of trees shadowed the house densely. 树丛把这幢房子遮蔽得很密实。
• We passed through miles of densely wooded country. 我们穿过好几英里茂密的林地。