VOA标准英语2014--科学家从南极苍蝇测定最小基因序列

 

Scientists Sequence Smallest Genome Ever With Antarctic Fly 科学家从南极苍蝇测定最小基因序列

Scientists have just sequenced the genome of a fly native to Antarctica, the coldest, driest and windiest place on the planet, a finding that may lead to a wider understanding of how these bugs² evolved to cope with the environment.

The fly, named Belgica antarctica, is a survivor³, or as Washington State University evolutionary⁴ biologist Joanna Kelley likes to put it…an extremophile.

“This fly has to withstand freezing, extreme temperature changes so in the Antarctic summer it’s on the rocks and those are getting quite hot," Kelley said. "But imagine the Antarctic winter, it’s very dark and cold. There’s a lot of UV [ultraviolet] radiation. There’s dehydration⁵.  And anything you can imagine as an extreme pressure, this fly probably encounters it.”    

Common fly

The fly is a midge, a group of small flies found practically everywhere on earth. 

This midge has evolved to survive in the extreme environment of the rocky outcrops of the Antarctic Peninsula.

It is wingless, so it can't be swept up by the wind and blown into the sea. It can also tolerate 40 percent or more water loss in its cells, more than double that of other midges.  

Kelley says the fly spends two years as larvae⁶ over two cold seasons.

“They look like dried up little raisins⁷ and that’s how they survive the winter," she said. "They are not developmentally active during that time, but they are still alive. This begs the question of, 'Does the small genome somehow enable them to go through that process, or the growing process in the summer more rapidly, or facilitate that somehow?'”  

Smallest bug¹ sequenced

Belgica antarctica is the first polar insect and the first freeze-tolerant insect whose genome - or genetic⁸ material - has been sequenced. 

It is also the smallest bug sequenced to date. Its genome has 99 million base pairs, the DNA⁹ building blocks of an organism. That's tiny compared with the human genome which has 3.2 billion base pairs. 

Kelley says the genome gives researchers a framework to study the organism in much more depth. For example, she says, they can look for what triggers its genes¹⁰ to activate¹¹ a protein in response to heat or cold stress.

“The heat shock proteins are important in this fly, particularly because they are expressed all the time," she said. "In other organisms, heat shock proteins, which are turned on in response to temperature or other stresses, in the fly they are turned on all the time. And this process may give us insight into how the fly is able to survive over the winter.”

Possible medical advances

Kelley says understanding how the freeze tolerant mechanism¹² works in a bug could lead to developments outside the insect world. 

The most direct human application, she says, might be in cryo-preservation or the freezing of human cells or tissues for medical purposes.

The study is published in the journal Nature Communications.

1 bug   

n.虫子；故障；窃听器；vt.纠缠；装窃听器

参考例句：

• There is a bug in the system.系统出了故障。
• The bird caught a bug on the fly.那鸟在飞行中捉住了一只昆虫。

2 bugs   

adj.疯狂的，发疯的n.窃听器( bug的名词复数 )；病菌；虫子；[计算机]（制作软件程序所产生的意料不到的）错误

参考例句：

• All programs have bugs and need endless refinement. 所有的程序都有漏洞，都需要不断改进。 来自《简明英汉词典》
• The sacks of rice were swarming with bugs. 一袋袋的米里长满了虫子。 来自《简明英汉词典》

3 survivor   

n.生存者，残存者，幸存者

参考例句：

• The sole survivor of the crash was an infant.这次撞车的惟一幸存者是一个婴儿。
• There was only one survivor of the plane crash.这次飞机失事中只有一名幸存者。

4 evolutionary   

adj.进化的；演化的，演变的；[生]进化论的

参考例句：

• Life has its own evolutionary process.生命有其自身的进化过程。
• These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。

5 dehydration   

n.脱水，干燥

参考例句：

• He died from severe dehydration.他死于严重脱水。
• The eyes are often retracted from dehydration.眼睛常因脱水而凹陷。

6 larvae   

n.幼虫

参考例句：

• Larvae are parasitic on sheep.幼虫寄生在绵羊的身上。
• The larvae prey upon small aphids.这种幼虫以小蚜虫为食。

7 raisins   

n.葡萄干( raisin的名词复数 )

参考例句：

• These raisins come from Xinjiang,they taste delicious. 这些葡萄干产自新疆，味道很甜。 来自《简明英汉词典》
• Mother put some raisins in the cake. 母亲在糕饼中放了一些葡萄干。 来自辞典例句

8 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

9 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。

10 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

11 activate   

vt.使活动起来，使开始起作用

参考例句：

• We must activate the youth to study.我们要激励青年去学习。
• These push buttons can activate the elevator.这些按钮能启动电梯。

12 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。