2014年经济学人 杀手在敲门 七个基因祸害无穷

A killer¹ in close up

You can do a lot of damage with just seven genes²

EBOLA is a simple virus, but also a subtle one. The stringy looking particles consist of a genome wrapped up in two layers of protein. This long, thin package, along with a large protein called a polymerase, is packed into a membrane³ that is studded with a glycoproteins—that is, proteins with sugar stuck to them.

When the virus infects a cell the polymerase makes copies of the genome and the cell is tricked into using these to make the proteins that the virus needs. These include two, called VP35 and VP24, which stymie⁴ interferons, a class of molecule⁵ that alerts the immune system to infection. VP35 prevents interferons from being made; VP24 stops their cries for help from being heard. The sugars on the virus's outside make it hard for other parts of the immune system to get to grips with; to confuse things more, the virus makes infected cells produce more glycoprotein than it needs for its coat, with the surplus simply secreted⁶ into the bloodstream. Antibodies which would otherwise attack the virus stick to this decoy protein instead.

Immune cells which the virus attacks in the bloodstream early on carry the infection to the liver, the spleen and lymph nodes. Symptoms may manifest themselves in a day or two or may wait weeks (see chart). Eventually the virus's spread triggers an immune overreaction known as a cytokine storm. Blood-vessel walls become leaky, blood pressure and core temperature drop, organs fail and the body goes into shock. Various combinations of those and other symptoms kill about 70% of those who get ill.

Some of the sick weather the storm, but most who survive infection do so by never getting to its direst straits. Some do not succumb⁷ at all: a study of people who had direct contact with patients during outbreaks in Gabon in 1996 showed that some had definitely been infected, but never fallen ill.

1 killer   

n.杀人者，杀人犯，杀手，屠杀者

参考例句：

• Heart attacks have become Britain's No.1 killer disease.心脏病已成为英国的头号致命疾病。
• The bulk of the evidence points to him as her killer.大量证据证明是他杀死她的。

2 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

3 membrane   

n.薄膜，膜皮，羊皮纸

参考例句：

• A vibrating membrane in the ear helps to convey sounds to the brain.耳膜的振动帮助声音传送到大脑。
• A plastic membrane serves as selective diffusion barrier.一层塑料薄膜起着选择性渗透屏障的作用。

4 stymie   

v.妨碍，阻挠

参考例句：

• Companies have been stymied by the length of time it takes to reach an agreement.由于耗时过长，各公司一直未能达成协议。
• Relief efforts have been stymied in recent weeks by armed gunmen.最近几周的救援工作一直受到武装分子的阻挠。

5 molecule   

n.分子，克分子

参考例句：

• A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈̬f婘̬ 妈̬成的。
• This gives us the structural formula of the molecule.这种方式给出了分子的结构式。

6 secreted   

v.（尤指动物或植物器官）分泌( secrete的过去式和过去分词 )；隐匿，隐藏

参考例句：

• Insulin is secreted by the pancreas. 胰岛素是胰腺分泌的。
• He secreted his winnings in a drawer. 他把赢来的钱藏在抽届里。 来自《简明英汉词典》

7 succumb   

v.屈服，屈从；死

参考例句：

• They will never succumb to the enemies.他们决不向敌人屈服。
• Will business leaders succumb to these ideas?商业领袖们会被这些观点折服吗？