跟读练习: CRISPR: Gene editing and beyond - 通过视频学习英语口语

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The CRISPR -Cas9 system is a tool for cutting DNA at a specifically targeted location.

The technique has already revolutionised gene editing, but scientists are always looking for new possibilities.

So what else can CRISPR do?

Since being discovered in a bacterial immune system, CRISPR -Cas9 has been adapted into a powerful tool for genomic research.

There are two components to the system, a DNA cutting protein called Cas9 and an RNA molecule known as the guide RNA.

Bound together they form a complex that can identify and cut specific sections of DNA.

First Cas9 has to locate and bind to a common sequence in the genome called a PAM.

Once the PAM is bound, the guide RNA unwinds part of the double helix.

The RNA strand is designed to match and bind a particular sequence in the DNA.

Once it's found the correct sequence, Cas9 can cut the DNA.

Its two nuclease domains each make a nick, leading to a double strand break.

Although the cell will try to repair this break, the fixing process is error -prone and often inadvertently introduces mutations that disable the gene.

This makes CRISPR a great tool for knocking out specific genes.

But making double strand breaks isn't all CRISPR can do.

Some researchers are deactivating one or both of Cas9's cutting domains and fusing new enzymes onto the protein.

Cas9 can then be used to transport those enzymes to a specific DNA sequence.

In one example, Cas9 is fused to an enzyme, a deaminase, which mutates specific DNA bases,

eventually replacing cytidine with thymidine.

This kind of precise gene editing means you could turn a disease -causing mutation into a healthy version of the gene, or introduce a stop codon at a specific place.

But it's not all about gene editing.

Several labs have been working on ways to use CRISPR to promote gene transcription.

They do this by deactivating Cas9 completely so it can no longer cut DNA.

Instead, transcriptional activators are added to the Cas9 by either fusing them directly or via a string of peptides.

alternatively the activators can be recruited to the guide RNA instead

these activators recruit the cells transcription machinery bringing RNA polymerase and other factors to the target and

increasing transcription of

that gene the same principle applies to genes silencing a crab

domain fused to the Cas9 inactivates transcription by recruiting more factors that physically block the gene.

A more outside the box idea for using CRISPR is to attach fluorescent proteins to the complex

so you can see where particular DNA sequences are found in the cell.

This could be useful for things like visualising the 3D architecture of the genome, or to paint an entire chromosome and follow its position in the nucleus.

CRISPR has already changed the face of research, but these new ideas show that what's been achieved

so far could just be the tip of the iceberg when it comes to CRISPR's potential.

Whatever comes next, it seems the CRISPR revolution is far from over.

Thank you.

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本课的词汇与口语要点

这节口语课以视频“CRISPR: Gene editing and beyond”为素材。视频中反复出现的词有：Cas, gene, Crispr, Dna, Rna。这段视频共有 35 个句子、509 个单词可供跟读。讲话部分时长为 4:20。说话人语速平稳，每分钟约 118 个词，很适合跟读。只有 69% 的单词属于英语最常用的 3,000 词，词汇难度较高。

视频中的重点词汇

视频中 15 个值得学习的单词，附发音和释义：

单词	发音	释义
gene 名词	/d͡ʒiːn/	基因
sequence 名词	/ˈsiː.kwəns/	序列, 順序 /顺序
fuse 名词	/fjuːz/	導火線 /导火线, 導火索 /导火索
domain 名词	/ˌdəʊˈmeɪ̯n/	領域 /领域
edit 动词	/ˈɛdɪt/	編輯 /编辑
recruit 动词	/ɹɪˈkɹut/	招聘, 徵兵 /征兵
enzyme 名词	/ˈɛn.zaɪm/	酶, 酵素
strand 名词	/ˈstɹænd/	綹 /绺, 一綹頭髮 /一绺头发
introduce 动词	/ˌɪntɹəˈdus/	介紹 /介绍, 紹介 /绍介
genome 名词	/ˈd͡ʒiː.noʊm/	基因組 /基因组, 基因體 /基因体
mutation 名词	/mjuˈteɪʃən/	突變 /突变, 變種 /变种
technique 名词	/tɛkˈniːk/	技術 /技术, 技巧
silence 名词	/ˈsaɪ̯ləns/	沉默
architecture 名词	/ˈɑː.kɪˌtɛk.t͡ʃə/	建築 /建筑, 建築學 /建筑学
repair 动词	/ˈɹiːpɛɚ/	修理

视频中出现的短语动词

单词	释义
knock out 动词	昏迷

视频中的语法

说话人最常用的结构，并附上视频中的原话：

结构	视频中的用法
被动语态 be + 过去分词 — 强调发生了什么，而不是谁做的	being discovered · is bound · is designed
现在完成时 have/has + 过去分词 — 过去发生但与现在仍有关联的事	has already revolutionised · has been adapted · has already changed

需要注意的发音

“sh” 和 “zh” 音: transcription /tɹænˈskɹɪpʃən/, mutation /mjuˈteɪʃən/, machinery /məˈʃiːnəɹi/
长单词——注意重音位置: architecture /ˈɑː.kɪˌtɛk.t͡ʃə/, machinery /məˈʃiːnəɹi/, alternatively /ɔlˈtɝ.nə.tɪv.li/, deactivate /ˌdiːˈæktɪveɪt/, deaminase /diːˈæmɪneɪz/

中文母语者容易读错的音：

/v/ — 不要读成 /w/，上齿轻触下唇: discover /dɪˈskʌvə/, alternatively /ɔlˈtɝ.nə.tɪv.li/, deactivate /ˌdiːˈæktɪveɪt/, inactivate /ɪˈnæktɪveɪt/
词尾辅音 — 要读清楚，后面不要加元音: sequence /ˈsiː.kwəns/, bind /ˈbaɪ̯nd/, fuse /fjuːz/, edit /ˈɛdɪt/, recruit /ɹɪˈkɹut/
/r/ 和 /l/ 的区别: principle /ˈpɹɪn.sɪ.pəl/, bacterial [bækˈtɪəɹiəɫ], fluorescent /flɔˈɹɛsənt/

如何用这段视频练习

先完整听一遍视频，不要开口，记下不认识的单词。
用正常速度逐句跟读，每句重复到你的节奏与说话人一致为止。
录下自己的声音并与原声对比，特别注意 gene, sequence, fuse 这类单词。

什么是跟读法？

跟读法 (Shadowing) 是一种有科学依据的语言学习技巧，最初开发用于专业口译员的培训，并由多语言者Alexander Arguelles博士普及。这个方法简单而强大：您在听英语母语原声的同时立即大声重复——就像是一个延迟1-2秒紧跟说话者的影子。与被动听力或语法练习不同，跟读法强迫您的大脑和口腔肌肉同时处理并模仿真实的讲话模式。研究表明它能显着提高发音准确性，语调，节奏，连读，听力理解和口语流利度——使其成为雅思口语备考和真实英语交流最有效的方法之一。

影子跟读法: 阅读完整分步指南 →

跟读练习: CRISPR: Gene editing and beyond - 通过视频学习英语口语

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