英语听力文摘 English Digest 712 遗传错误与大脑理论的秘密

Genetic² Error and the Big Brain Theory

When cells divide to create copies of themselves or to make sperm³ and eggs, there is always a chance of genetic error. Gene¹ duplication, when a regular gene is copied twice, is one of those mishaps⁴.

Gene duplication is usually detrimental⁵ and can lead to deformation⁶ and death if not caught by the cell’s repair machinery⁷. But in rare instances, it may also be evolutionarily important.

Brain Matters

Scientists researching genes⁸ important in brain development believe they have found duplication errors that reveal how the human brain increased in size during evolutionary⁹ history. While studying SRGAP2, a gene linked to epileptic seizures¹⁰, scientists found that the gene had not only duplicated once, but a number of times throughout human lineage.

Analysis of the SRGAP2 genes determined¹¹ that duplications occurred 3.4 and 2.4 million years ago, during which time chimp¹²?like ancestors were evolving into the first pre?humans and human?like ancestors.

Mutant Mice

To test the function of the duplicated genes, scientists inserted human copies into mice. The mice didn’t grow larger brains, but their brain cells looked more like human cells with thicker, longer and more numerous spines¹³ to connect with other neurons. The neurons also grew more quickly, suggesting they could migrate farther during development and enable the brain to become larger.

About 30 genes have undergone gene duplication since humans and chimps¹⁴ diverged¹⁵ from a common ancestor about six million years ago. Many of these genes control brain development. Researchers suspect that gene duplication is the key to unlocking the mysteries surrounding human brain evolution.

遗传错误与大脑理论的秘密

当细胞分裂产生自己的复制品或制造精子和卵子时，总有可能发生遗传错误。当一个普通基因被复制两次时，基因复制就是其中的一个不幸。

基因复制通常是有害的，如果不被细胞的修复机制捕获，会导致变形和死亡。但在极少数情况下，它可能在进化上也很重要。

大脑问题

研究大脑发育中重要基因的科学家认为，他们发现了重复错误，揭示了人类大脑在进化史中的大小是如何增加的。在研究与癫痫发作相关的基因SRGAP2时，科学家发现该基因不仅复制了一次，而且在整个人类谱系中复制了多次。

对SRGAP2基因的分析表明，复制发生在340万年和240万年前，黑猩猩在哪一时期？就像祖先进化成第一个祖先？人类和人类？就像祖先一样。

突变小鼠

为了测试复制基因的功能，科学家将人类复制品插入小鼠体内。这些小鼠的大脑并没有长得更大，但它们的脑细胞看起来更像人类的细胞，具有更厚、更长和更多的棘，可以与其他神经元连接。神经元也生长得更快，这表明它们在发育过程中可以迁移得更远，从而使大脑变得更大。

自从大约600万年前人类和黑猩猩从一个共同的祖先分化出来以来，大约有30个基因经历了基因复制。其中许多基因控制着大脑的发育。研究人员怀疑，基因复制是解开人类大脑进化之谜的关键。

1 gene   

n.遗传因子，基因

参考例句：

• A single gene may have many effects.单一基因可能具有很多种效应。
• The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。

2 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。

3 sperm   

n.精子，精液

参考例句：

• Only one sperm fertilises an egg.只有一个精子使卵子受精。
• In human reproduction,one female egg is usually fertilized by one sperm.在人体生殖过程中，一个精子使一个卵子受精。

4 mishaps   

n.轻微的事故，小的意外( mishap的名词复数 )

参考例句：

• a series of mishaps 一连串的倒霉事
• In spite of one or two minor mishaps everything was going swimmingly. 尽管遇到了一两件小小的不幸，一切都进行得很顺利。 来自《现代汉英综合大词典》

5 detrimental   

adj.损害的，造成伤害的

参考例句：

• We know that heat treatment is detrimental to milk.我们知道加热对牛奶是不利的。
• He wouldn't accept that smoking was detrimental to health.他不相信吸烟有害健康。

6 deformation   

n.形状损坏；变形；畸形

参考例句：

• The deformation frequencies are not sufficiently distinctive.其变形频率不是十分明显的。
• The calculated deformation is almost equal to the real situation by measurement.经检测，计算变形量与实际情况基本一致。

7 machinery   

n.(总称)机械，机器；机构

参考例句：

• Has the machinery been put up ready for the broadcast?广播器材安装完毕了吗？
• Machinery ought to be well maintained all the time.机器应该随时注意维护。

8 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

9 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。

10 seizures   

n.起获( seizure的名词复数 )；没收；充公；起获的赃物

参考例句：

• Seizures of illicit drugs have increased by 30% this year. 今年违禁药品的扣押增长了30%。 来自《简明英汉词典》
• Other causes of unconsciousness predisposing to aspiration lung abscess are convulsive seizures. 造成吸入性肺脓肿昏迷的其他原因，有惊厥发作。 来自辞典例句

11 determined   

adj.坚定的；有决心的

参考例句：

• I have determined on going to Tibet after graduation.我已决定毕业后去西藏。
• He determined to view the rooms behind the office.他决定查看一下办公室后面的房间。

12 chimp   

n.黑猩猩

参考例句：

• In fact,the color of gorilla and chimp are light-color.其实大猩猩和黑猩猩的肤色是较为浅的。
• The chimp is the champ.猩猩是冠军。

13 spines   

n.脊柱( spine的名词复数 )；脊椎；（动植物的）刺；书脊

参考例句：

• Porcupines use their spines to protect themselves. 豪猪用身上的刺毛来自卫。
• The cactus has spines. 仙人掌有刺。 来自《现代英汉综合大词典》

14 chimps   

（非洲）黑猩猩( chimp的名词复数 )

参考例句：

• Chimps are too scarce, and too nearly human, to be routinely slaughtered for spare parts. 黑猩猩又太少，也太接近于人类，不可以作为人器官备用件说杀就杀。 来自英汉非文学 - 生命科学 - 医学的第四次革命
• And as nonprimates, they provoke fewer ethical and safety-related concerns than chimps or baboons. 而且作为非灵长类，就不会产生像用黑猩猩或狒狒那样的伦理和安全方面的顾虑。 来自英汉非文学 - 生命科学 - 医学的第四次革命

15 diverged   

分开( diverge的过去式和过去分词 )； 偏离； 分歧； 分道扬镳

参考例句：

• Who knows when we'll meet again? 不知几时咱们能再见面！
• At what time do you get up? 你几时起床？