Maybe it's your phone, your laptop, your drawing tablet, but for me, it is the copy machine.

也許它是你的手機、筆記本電腦、繪圖板，但對我來說，它就是複印機。

Oh, the copy machine.

哦，複印機。

I know it's not possible, but I can promise you that whenever the copy machine was aware of my presence, that's when it decided to malfunction.

我知道這不可能，但我可以向你保證，每當複印機意識到我的存在時，就是它決定出故障的時候。

Especially if it knew I was short on time.

尤其是當它知道我時間不多的時候。

And of course, when it jams, the fancy copy machines will even tell you what is wrong and how to fix it, but my experience with trying to follow the instructions of fixing the copy machine makes it worse, and then by that point, there's a line, and you feel your heart pounding, and you're embarrassed because now you've jammed it for everyone.

當然，當複印機卡紙時，高級複印機甚至會告訴你出了什麼問題以及如何修理，但我的經驗是，如果試圖按照修理複印機的說明去做，情況就會更糟，到那時，就會出現排隊現象，你會感到心怦怦直跳，你會感到很尷尬，因為現在你已經為大家把複印機卡住了。

Yeah, so while I've developed an appreciation and respect for the copy machine, I've definitely tried to limit my use of it over the years.

是的，雖然我對複印機充滿了感激和敬意，但多年來我一直儘量少用它。

Saves paper, anyway.

總之可以節省紙張。

You may be wondering why is she spending so much time on this?

你可能會問，她為什麼要花這麼多時間在這上面？

Well, I want to call your attention to a technology, a biotechnology, that works almost like an amazing, and fancy, copy machine.

好吧，我想提請你們注意一種技術，一種生物技術，它的工作原理幾乎就像一臺神奇而華麗的複印機。

Except not for something on paper.

除了紙上的東西。

No, it's for DNA.

不，這是為了 DNA。

This biotechnology is PCR, Polymerase Chain Reaction, or PCR for short.

這種生物技術就是 PCR，即聚合酶鏈式反應，簡稱 PCR。

It provides a way to make more copies of a portion of DNA.

它提供了一種複製更多 DNA 部分的方法。

Lots and lots and lots of DNA copies, and this technology does not need to happen in a cell either.

大量、大量、大量的 DNA 副本，而且這種技術也不需要在細胞內進行。

In fact, it can happen in a test tube.

事實上，它可以在試管中發生。

And so you may wonder, number one, how does PCR work, and number two, why?

你可能會問，第一，PCR 是如何工作的；第二，為什麼？

Why make more copies of some specific portion of DNA?

為什麼要複製更多的 DNA 特定部分？

So let's briefly answer those two questions.

那麼，讓我們來簡要回答這兩個問題。

To answer the first question, the how does this work question, let's talk about what we need first before we get to the steps of how it works.

要回答第一個問題，即 "如何工作 "的問題，我們先來談談我們需要什麼，然後再討論如何工作。

We need the DNA portion that we want to make copies of.

我們需要複製 DNA 部分。

We need some kind of buffer to put it in, and then we need things that would be necessary to make more copies of the DNA.

我們需要某種緩衝劑來把它放進去，然後我們還需要一些東西來製作更多的 DNA 副本。

So think about what that might mean from our DNA replication video.

所以，從我們的 DNA 複製視頻中想想這可能意味著什麼。

We'll need primers.

我們需要底漆。

We're called it primers, help DNA polymerase, a building enzyme, know where to go to start its building.

我們稱之為引物，它能幫助 DNA 聚合酶這種構建酶知道從哪裡開始構建。

We need DNA polymerase, the building enzyme.

我們需要 DNA 聚合酶這種構建酶。

Fun fact, the DNA polymerase used is often a heat-resistant type of DNA polymerase as PCR uses heat.

有趣的是，由於 PCR 需要加熱，是以使用的 DNA 聚合酶通常是一種耐熱型 DNA 聚合酶。

Typically, the polymerase chosen for the job is Taq polymerase, a type of heat-resistant DNA polymerase.

通常情況下，選用的聚合酶是 Taq 聚合酶，這是一種耐熱 DNA 聚合酶。

Taq polymerase is originally from a type of bacteria that can handle and live in really high temperatures in nature, in hot springs.

Taq 聚合酶最初來自一種細菌，這種細菌可以在自然界的高溫環境中（如溫泉）生存。

Pretty cool.

太酷了

We also need DNA nucleotides for the DNA polymerase to build with.

我們還需要 DNA 核苷酸供 DNA 聚合酶構建。

So we can look at the PCR sequence in three major steps.

是以，我們可以將 PCR 序列分為三個主要步驟。

We'll illustrate with one double-stranded DNA molecule here, and let's assume this is what we want replicated.

我們以一個雙鏈 DNA 分子為例進行說明，假設這就是我們想要複製的東西。

Step 1.

步驟 1.

Denaturation.

變性。

You've heard that word denature before, right?

你聽說過變性這個詞吧？

When we were talking about enzymes?

當我們談論酶的時候？

One way we had talked about denaturing enzymes was using heat, and heat is what we will use in this step.

我們曾討論過一種使酶變性的方法，那就是加熱。

This step involves the addition of heat needed to separate the two strands of the DNA molecule.

這一步驟需要加熱，以分離 DNA 分子的兩條鏈。

Step 2.

步驟 2.

Annealing.

退火。

Okay, so this word means something a little different in biology.

好吧，這個詞在生物學中的含義有點不同。

Basically, this is when the two DNA strands that now have been separated by that heat are going to be cooled and be joined by the primers.

基本上，這時被熱量分開的兩條 DNA 鏈將被冷卻，並通過引物連接起來。

The temperature for this step should allow the primers to bind to the specific segment of DNA that you want to amplify, which means make copies of.

這一步驟的溫度應允許引物與要擴增（即複製）的特定 DNA 片段結合。

Step 3.

步驟 3.

DNA synthesis.

DNA 合成。

Remember, synthesis means to make something.

記住，"合成 "的意思是製造某種東西。

With DNA synthesis, we're going to make more copies of DNA, and to do so, DNA polymerase will begin to work on both of these strands and it will use the DNA nucleotides as its building material to amplify the DNA.

通過 DNA 合成，我們將製造更多的 DNA 副本，為此，DNA 聚合酶將開始在這兩條鏈上工作，它將使用 DNA 核苷酸作為構建材料來擴增 DNA。

We should note that the temperature at this step may be a little warmer than the previous step.

需要注意的是，這一步的溫度可能會比上一步稍高一些。

It needs to be a temperature that is ideal for the specific DNA polymerase used.

溫度必須是所用特定 DNA 聚合酶的理想溫度。

Now after finishing one cycle of this, you have two double-stranded DNA molecules, right?

完成一個循環後，就有了兩個雙鏈 DNA 分子，對嗎？

Similar to how it would be in DNA replication within a cell.

類似於 DNA 在細胞內的複製過程。

But you can repeat this now, except this time, you now have two double-stranded DNA molecules to start with.

但你現在可以重複這個過程，只不過這次你有了兩個雙鏈 DNA 分子。

So you repeat with the denaturation, annealing, and DNA synthesis steps.

是以，需要重複變性、退火和 DNA 合成步驟。

Now you have four double-stranded DNA molecules.

現在你有了四個雙鏈 DNA 分子。

You repeat the steps again.

再次重複這些步驟。

Now you have eight.

現在你有八個。

And if the process is automated by a machine, which, why yes, they do have in science catalogs, you can actually do this fairly quickly.

如果這個過程是由機器自動完成的，而科學目錄中確實有這樣的機器，那麼實際上你可以相當快地完成這個過程。

Which brings you to why?

為什麼？

Why do this?

為什麼要這樣做？

Well, any technology that needs copies of a portion of DNA could find PCR useful, but we'll just mention two examples in our limited time.

當然，任何需要拷貝部分 DNA 的技術都能找到 PCR 的用武之地，但在有限的時間內，我們只舉兩個例子。

We mentioned DNA fingerprinting in our gel electrophoresis video.

我們在凝膠電泳視頻中提到了 DNA 指紋。

And we mentioned that DNA fingerprinting can be part of a crime scene investigation.

我們還提到，DNA 指紋鑑定可以作為犯罪現場調查的一部分。

Well, in order to have enough copies of DNA samples to run in gel electrophoresis to analyze, PCR can be performed to make copies of the fragments of DNA that are found at a crime scene.

為了獲得足夠的 DNA 樣本副本，以便在凝膠電泳中進行分析，可以通過 PCR 來複制在犯罪現場發現的 DNA 片段。

Another example?

另一個例子呢？

Diagnosis of a disease, such as one caused by a virus.

疾病診斷，例如由病毒引起的疾病。

For an especially relevant example, I can mention one of the testing types done for the virus that causes COVID-19.

舉一個特別相關的例子，我可以提到針對導致 COVID-19 的病毒所做的一種測試。

COVID-19 is a pandemic that we're experiencing right now in 2020.

COVID-19 是我們現在正在經歷的 2020 年大流行病。

And the virus that causes COVID-19 is called SARS-CoV-2.

而導致 COVID-19 的病毒被稱為 SARS-CoV-2。

You might have heard of one test type that uses a sample from a nose or throat swab in a PCR test.

您可能聽說過一種檢測方法，即使用鼻腔或咽喉拭子樣本進行 PCR 檢測。

But to be more specific, this test for this virus is a real-time reverse transcription PCR test.

但更具體地說，這種病毒的檢測是一種實時反轉錄 PCR 檢測。

The reason it has this fancier reverse transcription in there is because this virus uses RNA as its genetic material instead of DNA.

之所以有這種更高級的反轉錄，是因為這種病毒使用 RNA 而不是 DNA 作為遺傳物質。

And you have to use an enzyme called reverse transcriptase to convert the RNA into DNA.

你必須使用一種叫做逆轉錄酶的酶，將 RNA 轉換成 DNA。

So before we can do the regular PCR steps we've mentioned, we must convert isolated and purified RNA into DNA.

是以，在進行我們提到的常規 PCR 步驟之前，我們必須將分離純化的 RNA 轉化為 DNA。

A specific primer is added that will bind to an area of viral RNA, and then reverse transcriptase is used to convert viral RNA into cDNA, complementary DNA.

加入的特定引物會與病毒 RNA 的某個區域結合，然後使用逆轉錄酶將病毒 RNA 轉化為 cDNA（互補 DNA）。

Using specific primers and the Taq DNA polymerase, the cDNA can be copied over and over each cycle in the familiar steps we've been mentioning of PCR.

利用特定的引物和 Taq DNA 聚合酶，cDNA 可以按照我們熟悉的 PCR 步驟反覆複製。

See, the goal is you need enough copies of the viral cDNA in order for it to be detectable.

你看，我們的目標是需要足夠多的病毒 cDNA 拷貝，這樣才能檢測到病毒。

The idea being, if it's a positive result, you have the selective primers binding and you have the Taq DNA polymerase making more and more copies of the viral cDNA each cycle.

這樣做的目的是，如果結果呈陽性，就說明選擇性引物已經結合，Taq DNA 聚合酶會在每個循環中製造越來越多的病毒 cDNA 副本。

In addition, specific fluorescent probes are also used for identification.

此外，特定的熒光探針也可用於鑑定。

A certain level is needed for identification of a positive result.

陽性結果的鑑定需要一定的水準。

And if the virus' genetic material is not present in the sample, then primers wouldn't bind and there would be no cDNA copies produced.

如果樣本中不存在病毒的遺傳物質，那麼引物就不會結合，也就不會產生 cDNA 副本。

If you'd like to learn more about this test as far as its limitations and also its complexity as we're being pretty general here, we've included some further reading suggestions in the video details.

如果您想進一步瞭解這項測試的侷限性和複雜性，我們在視頻詳情中提供了一些進一步閱讀的建議。

So those were just two examples of how PCR can be used, but there are many more examples in our suggested further reading links in the video description.

以上只是 PCR 使用方法的兩個例子，更多例子請參見視頻描述中的 "建議進一步閱讀 "鏈接。

Overall, PCR is such a useful and fascinating technology that will likely remain indispensable for future uses.

總之，PCR 是一項非常有用和迷人的技術，在未來的應用中仍將不可或缺。

And it's a rare day when I pull out that word indispensable.

難得有一天，我說出了 "不可或缺 "這個詞。

Well, that's it for the Amoeba Sisters and we remind you to stay curious.

阿米巴姐妹》到此結束，我們提醒大家保持好奇心。

Bye for now.

再見。