跟读练习: High Resolution Melting (HRM) analysis made easy. - 通过视频学习英语口语
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High resolution melting
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or HRM is a very sensitive method to detect sequence variation
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in different samples up to a resolution of a single base pair without the need of sequencing.
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Here you see a wild type of DNA or a PCR product.
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After mutation you may get a homozygous mutant in
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which both the alleles are mutated or a heterozygous mutant in which a single allele is mutated.
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Now you want to check if mutation is there or not.
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HRM is based upon the principle of DNA dissociation with increase in temperature followed by detection by a fluorescent dye.
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The DNA denituration is based on the GC content.
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Higher the GC content, stronger will be the DNA bonds and higher will be the melting temperature to dissociate the two strands.
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In HRM, the detection is assisted by specific binding of a saturating fluorescent dye to the double-stranded DNA
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and measuring its fluorescence in real time on increasing the temperature gradually.
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For HRM, you need to PCR amplify your target gene locus to obtain a specific amplicon.
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Smaller the size of amplicon, better the results will be.
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Then you add a saturating fluorescent dye
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that binds to the dna only in the double stranded form
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then you proceed for hrm analysis in a real time machine here you gradually increase the temperature
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and fluorescence is measured simultaneously the plot shows fluorescence in the y-axis and temperature on the x-axis
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3 different curves are obtained for wild, homozygous and heterozygous mutant.
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Here you see as homozygous mutant had a GC mutation as seen in the previous slide its TM is higher.
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So the curve shifts towards the right.
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Heterozygous mutant on the other hand have a mutation in only one strand.
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So it has a base mismatch and hence the TM is reduced and the curve shifts towards the left.
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method is so sensitive that it detects the variation in the melting temperature up to 0.2 degree Celsius.
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HRM being a simple, economic, rapid and precise method of DNA variant detection, it can be used for mutant identification,
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SNP genotyping, DNA methylation by bisulfide sequencing, DNA fingerprinting and so on.
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This video has been made on a special request by Ms. Sahily Russell.
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本课的词汇与口语要点
这段视频共有 27 个句子、373 个单词可供跟读。 讲话部分时长为 2:30。 说话人语速平稳，每分钟约 149 个词，很适合跟读。 只有 66% 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 |
|---|---|---|
| mutant 名词 | /ˈmju(t)n̩(t)/ | 突變體 /突变体 |
| strand 名词 | /ˈstɹænd/ | 綹 /绺, 一綹頭髮 /一绺头发 |
| mutation 名词 | /mjuˈteɪʃən/ | 突變 /突变, 變種 /变种 |
| sequence 名词 | /ˈsiː.kwəns/ | 序列, 順序 /顺序 |
| curve 名词 | /kɚv/ | 彎子 /弯子 |
| melt 动词 | /mɛlt/ | 融化, 熔化 |
| sensitive 形容词 | /ˈsɛn.sɪt.ɪv/ | 敏感 |
| obtain 动词 | /əbˈteɪn/ | 獲得 /获得 |
| gradually 副词 | /ˈɡɹæd͡ʒuəli/ | 逐漸 /逐渐, 漸漸 /渐渐 |
| variation 名词 | /ˌvɛəɹiˈeɪʃn̩/ | 變化 /变化, 變動 /变动 |
| detect 动词 | /dɪˈtɛkt/ | 察覺 /察觉, 發覺 /发觉 |
| axis 名词 | /ˈæksɪs/ | 軸 /轴, 軸心 /轴心 |
| assist 动词 | /əˈsɪst/ | 幫 /帮, 幫助 /帮助 |
| hence 副词 | /ˈhɛns/ | 從這裡 /从这里, 從這兒 /从这儿 |
| rapid 形容词 | /ˈɹæp.ɪd/ | 快, 迅速 |
需要注意的发音
- “sh” 和 “zh” 音: mutation /mjuˈteɪʃən/, detection /dɪˈtɛk.ʃən/, variation /ˌvɛəɹiˈeɪʃn̩/, identification /aɪˌdɛn(t)ɪfɪˈkeɪʃn̩/, dissociate /dɪˈsoʊ.ʃi.eɪt/
- 长单词——注意重音位置: identification /aɪˌdɛn(t)ɪfɪˈkeɪʃn̩/, simultaneously /ˌsaɪmlˈteɪnɪəsli/, homozygous /ˌhəʊməʊˈzaɪɡəs/, dissociate /dɪˈsoʊ.ʃi.eɪt/, dissociation /dɪˌsoʊsiˈeɪʃən/
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 mutant, strand, mutation 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。