Have you ever wondered how we got here?

你有沒有想過，我們是怎麼來到這裡的？

Well, about 4.5 billion years ago, the Earth was a big ball of flame and rocks, constantly bombarded by even more rocks from space.

大約 45 億年前，地球是一個由火焰和岩石組成的大球，不斷受到來自太空的更多岩石的轟擊。

Fun fact, those rocks probably had some water inside them, which has now turned into steam.

有趣的是，這些岩石裡面可能有水，現在已經變成了蒸汽。

Breaking news, the Earth is cooling down.

最新消息，地球正在降溫。

Oh yeah, did I mention that- Whoops, everything's flooded.

哦，對了，我有沒有說過--哎呀，所有東西都被水淹了。

But hey, at least there's some cool stuff at the bottom, like hydrothermal vents, which are piping hot and filled with a bunch of chemicals that can make some very interesting stuff.

不過，至少海底有一些很酷的東西，比如熱液噴口，那裡熱氣騰騰，充滿了各種化學物質，可以製造出一些非常有趣的東西。

Wait a minute, what the heck is going on here?

等等，這到底是怎麼回事？

Biology is the study of life, but really, it's just chemistry in disguise.

生物學是一門研究生命的學科，但實際上，它只是變相的化學。

I mean, you and I are basically just a big ball of molecules that can make funny sounds.

我的意思是，你和我基本上就是一個能發出怪聲的大分子球。

Carbohydrates, lipids, proteins, and nucleic acids are some of the molecules that are fundamental to life.

碳水化合物、脂類、蛋白質和核酸是生命的基本分子。

Carbohydrates give you quick energy, lipids store long-term energy and make membranes, proteins make up tissues, and nucleic acids make DNA.

碳水化合物能快速提供能量，脂類能長期儲存能量並製造細胞膜，蛋白質能組成組織，核酸能製造 DNA。

Also, to make all the chemical reactions possible, living beings have inside of them a bunch of enzymes.

此外，為了使所有化學反應成為可能，生物體內有許多酶。

They're special proteins that act as catalysts, which just means they help chemical reactions speed up by either breaking down or combining one specific thing.

它們是一種特殊的蛋白質，可以起到催化劑的作用，也就是說，它們可以通過分解或結合一種特定的物質來幫助加快化學反應。

For example, lactase breaks down lactose, the sugar found in milk.

例如，乳糖酶能分解牛奶中的乳糖。

Okay, so enzymes make life possible by speeding up chemical reactions, but what even is life?

好吧，酶通過加快化學反應使生命成為可能，但生命到底是什麼呢？

Scientists don't really seem to agree, but obviously a cat is different from a rock.

科學家們的看法似乎並不一致，但顯然貓和石頭是不同的。

The cat can produce energy by metabolizing food, it can grow and develop, reproduce, and it responds to the environment, whereas the rock does not.

貓可以通過食物新陳代謝產生能量，可以生長髮育、繁殖，並對環境做出反應，而石頭卻不能。

Also, unlike rocks, every living thing on Earth is made of cells, of which there's two main categories, eukaryotes and prokaryotes.

此外，與岩石不同，地球上的所有生物都是由細胞組成的，其中有兩大類，即真核生物和原核生物。

Eukaryotes have fancy organelles which are bound by membranes, like the nucleus inside of which is DNA.

真核生物擁有由膜結合的奇特細胞器，如細胞核，核內有 DNA。

Prokaryotes have none of those organelles, and the DNA is just kind of chilling there, like, freely floating around.

原核生物沒有這些細胞器，DNA只是在那裡冷藏，就像自由漂浮一樣。

This is why prokaryotes are just single-cell organisms like bacteria and archaea, whereas eukaryotes can form complex organisms like protists, fungi, plants, and animals.

這就是為什麼原核生物只是細菌和古細菌等單細胞生物，而真核生物卻能形成原生生物、真菌、植物和動物等複雜生物的原因。

These are what's known as kingdoms, which is a taxonomic rank, so basically how we classify different living things and how they're related to one another.

這些就是所謂的 "王國"（kingdoms），這是分類學上的等級，基本上就是我們對不同生物的分類，以及它們之間的關係。

Because there are quite a few species of life on this planet, and naming them cat, dangerous cat, and water cat wouldn't really be all that helpful, we also give every species a unique and unambiguous scientific name consisting of the genus and the species.

因為地球上的生物種類很多，給它們分別命名為貓、危險貓和水貓並沒有什麼用處，所以我們也給每個物種起了一個獨特而明確的學名，其中包括屬和種。

One thing every species has in common is homeostasis, a.k.a. keeping certain conditions in check so you don't die.

每個物種都有一個共同點，那就是 "平衡"，也就是保持一定的狀態，以免死亡。

If you feel warm, your body will sweat.

如果你感到溫暖，身體就會出汗。

If you're cold, your body will shiver.

如果你很冷，你的身體就會顫抖。

A cell does kind of the same thing, just that it balances out concentrations of certain chemicals.

細胞也做著同樣的事情，只是它能平衡某些化學物質的濃度。

You see, enzymes, for example, only work in a very specific environment, let's say some specific pH value.

例如，酶只能在非常特殊的環境下工作，比方說，在特定的 pH 值下工作。

If this changes too much, the enzymes will denature and won't work anymore.

如果變化太大，酶就會變性，不再起作用。

To counter this, the cell needs to constantly keep up this specific pH value, which is controlled by the concentration of acid and base molecules.

為了應對這種情況，細胞需要不斷保持特定的 pH 值，而 pH 值是由酸分子和鹼分子的濃度控制的。

Okay, but like, how does the cell do that?

好吧，但細胞是怎麼做到的？

The secret lies in the cell membrane.

祕密在於細胞膜。

You see, it's a semi-permeable phospholipid bilayer- Okay, that's way too many words.

你看，它是一種半滲透性磷脂雙分子層--好吧，說得太多了。

All it is, is two layers of these funky looking molecules with a polar head and a non-polar tail.

它就是兩層看起來很奇怪的分子，有極性的頭部和非極性的尾部。

This allows small molecules like water and oxygen to slip right through, whereas larger particles like ions need special channels that can be opened or closed, which gives the cell control of what goes in and out.

這使得水和氧氣等小分子可以直接通過，而離子等大分子則需要可以打開或關閉的特殊通道，從而使細胞可以控制進出的物質。

Naturally, particles move with the gradient, so from a place of high concentration to a place of low concentration.

自然，粒子會隨著梯度移動，是以會從濃度高的地方移動到濃度低的地方。

Or, in the case of water, it can also move to a place of high solute concentration.

或者，就水而言，它也可以移動到溶質濃度高的地方。

So, for example, salt.

例如，鹽。

Welcome to Biology Pro Tips Season 1!

歡迎來到《生物學專業技巧》第一季！

Tip of the day, do not drink too much salt water.

今日提示：不要喝太多鹽水。

There's a bunch of salt in salt water.

鹽水中含有大量鹽分。

In fact, more salt than inside of a cell, which means it will draw water from your cells and dehydrate you.

事實上，鹽分比細胞內的鹽分還多，這意味著它會從細胞中吸取水分，使人脫水。

Yeah, that's it.

對，就是這樣。

Have a great day.

祝你愉快

Anyway, the process of balancing out gradients is known as diffusion and happens automatically.

總之，平衡梯度的過程被稱為擴散，是自動發生的。

But, by using a little bit of energy, particles can actively be moved against the gradient.

但是，只要使用一點能量，粒子就能主動逆著梯度移動。

The energy comes from adenosine triphosphate, or ATP.

能量來自三磷酸腺苷，即 ATP。

To be exact, the highly energetic chemical bonds between the phosphate groups can be broken to obtain energy.

確切地說，磷酸基團之間的高能化學鍵可以被破壞，從而獲得能量。

This is kind of important, as in, every organism and every cell needs to make ATP.

這一點非常重要，因為每個生物體和每個細胞都需要製造 ATP。

For example, through cellular respiration, which happens in the mitochondria.

例如，通過線粒體進行的細胞呼吸。

Together with oxygen, glucose, so sugar, is turned into water, carbon dioxide, and ATP.

葡萄糖（即糖）與氧氣一起轉化為水、二氧化碳和 ATP。

This is nice, but it only works if you already have glucose.

這很好，但只有在已經有葡萄糖的情況下才會起作用。

Humans are heterotrophs.

人類是異養生物。

They eat food, inside of which is sugar, which is then broken down into glucose.

它們吃食物，食物中含有糖分，然後被分解成葡萄糖。

Plants, on the other hand, are autotrophs.

而植物則是自養生物。

Simply put, they said, screw food, I'll just make my own glucose by staring at the sun.

簡而言之，他們說，去他媽的食物，我就盯著太陽自己製造葡萄糖。

You see, plant cells have smaller gonads called chloroplasts, inside of which is chlorophyll, which absorbs red and blue light, but reflects green light, which is why most plants look green.

你看，植物細胞有一個較小的性腺，叫做葉綠體，裡面有葉綠素，葉綠素吸收紅光和藍光，但反射綠光，這就是為什麼大多數植物看起來都是綠色的。

The absorbed energy from light is used to split water and make a special form of carbon dioxide, which can then be turned into glucose and oxygen.

從光中吸收的能量被用來分裂水和製造一種特殊形式的二氧化碳，然後將其轉化為葡萄糖和氧氣。

Okay, quick recap.

好了，簡單回顧一下。

Once you have glucose, either from food or photosynthesis, you can do cellular respiration to get energy in the form of ATP.

一旦從食物或光合作用中獲得葡萄糖，就可以進行細胞呼吸，獲得 ATP 形式的能量。

Chemically, ATP is what's known as a nucleotide.

在化學上，ATP 是一種核苷酸。

It has a phosphate group, a 5-carbon sugar, and a nitrogenous base.

它有一個磷酸基、一個 5 碳糖和一個氮基。

You know what else is made of nucleotides?

你知道還有什麼是由核苷酸組成的嗎？

Deoxyribonucleic acid, or DNA.

脫氧核糖核酸，即 DNA。

It consists of two strands of nucleotides, with the sugar and phosphate groups, but the actually important part is the nitrogenous base, which comes in four flavors.

它由兩股核苷酸組成，含有糖基和磷酸基，但真正重要的部分是含氮鹼基，有四種味道。

Adenine, thymine, cytosine, and guanine.

腺嘌呤、胸腺嘧啶、胞嘧啶和鳥嘌呤。

These bases can form base pairs through hydrogen bonds, where adenine goes with thymine and cytosine goes with guanine.

這些鹼基可以通過氫鍵形成鹼基配對，其中腺嘌呤與胸腺嘧啶配對，胞嘧啶與鳥嘌呤配對。

These bonds are what holds the two strands of DNA together.

這些鍵將 DNA 的兩條鏈連接在一起。

Okay, that's cool, I guess, but like, how the heck does that store genetic information?

好吧，這很酷，我想，但是，這到底是怎麼儲存基因資訊的呢？

I'm glad you ask.

很高興你這麼問。

A gene is a section of this DNA that codes for a special trait by carrying a certain sequence of base pairs, which is like a recipe for making a protein.

基因是 DNA 中的一個部分，它通過攜帶特定的鹼基對序列來編碼一種特殊的性狀，就像是製造蛋白質的配方。

Why proteins?

為什麼是蛋白質？

Because they're like, really important.

因為它們真的很重要

They transport molecules, act as enzymes, and determine the way you look.

它們能運輸分子、發揮酶的作用，還能決定你的容貌。

For example, the difference between brown and blue eyes is the amount of a pigment called melanin in the cells of the iris.

例如，棕色眼睛和藍色眼睛的區別在於虹膜細胞中一種叫做黑色素的色素的含量。

The OCA2 gene codes for P protein, which we believe controls the amount of melanin in cells, meaning that the proteins made from this gene could be what determines your eye color.

OCA2 基因編碼 P 蛋白，我們認為 P 蛋白控制著細胞中黑色素的數量，這意味著由該基因產生的蛋白質可能決定了你眼睛的顏色。

Pretty cool!

太酷了

There's just one issue.

只有一個問題。

Your DNA and its information is in the nucleus, but proteins are made in organelles called the ribosomes.

DNA 及其資訊在細胞核中，但蛋白質是在稱為核糖體的細胞器中製造的。

How do we get the information from A to B?

我們如何將資訊從 A 傳輸到 B？

The answer is RNA.

答案就是 RNA。

It's kind of like DNA, just that it's most often a single strand.

它有點像 DNA，只是最常見的是單鏈。

It uses ribose instead of deoxyribose, and instead of thymine, it uses uracil, which makes it less stable.

它使用的是核糖而不是脫氧核糖，使用的是尿嘧啶而不是胸腺嘧啶，是以穩定性較差。

But that's besides the point.

但這不是重點。

Here's what RNA actually does.

下面是 RNA 的實際作用。

Let's say you want to make the protein coded for by this gene.

比方說，你想製造這種基因編碼的蛋白質。

An enzyme called RNA polymerase will split the DNA and make a strand of RNA with a complementary basis, essentially copying the information from the DNA to the RNA.

一種名為 RNA 聚合酶的酶會分裂 DNA，並生成一條具有互補基礎的 RNA 鏈，從而將 DNA 中的資訊複製到 RNA 中。

This is called transcription.

這就是轉錄。

The new strand is called messenger RNA, or mRNA, because it carries this message out of the nucleus to a ribosome.

新鏈被稱為信使 RNA 或 mRNA，因為它將這一資訊帶出細胞核，傳遞給核糖體。

Remember how I said that a gene is like a recipe for a protein?

還記得我說過基因就像蛋白質的配方嗎？

Well, on the mRNA, which carries the same base sequence as that gene, every group of three bases, which is called a codon, codes for a specific amino acid, which are the building blocks for proteins.

那麼，在攜帶與該基因相同鹼基序列的 mRNA 上，每三個鹼基組（稱為密碼子）編碼一個特定的氨基酸，這些氨基酸是蛋白質的組成成分。

These amino acids are carried by special molecules called transfer RNA, or tRNA, which have a unique anticodon that can only attach to its matching codon on the mRNA.

這些氨基酸由名為轉移核糖核酸或 tRNA 的特殊分子攜帶，tRNA 有一個獨特的反密碼子，只能連接到 mRNA 上與其匹配的密碼子上。

The job of the ribosome is to read over codons on the mRNA and attach the matching tRNA molecules, which then leave behind their amino acid.

核糖體的工作是讀取 mRNA 上的密碼子，並連接匹配的 tRNA 分子，然後留下氨基酸。

As the ribosome moves along the mRNA and attaches more tRNA, which happens a couple thousand times, the amino acids combine into a polypeptide chain, which is just a really long chain of amino acids that can be bunched up, creased, smacked, and folded into a protein.

當核糖體沿著 mRNA 移動並連接更多的 tRNA（這種情況會發生幾千次）時，氨基酸就會結合成多肽鏈，而多肽鏈就是一條很長的氨基酸鏈，可以捆綁、折皺、抽打併摺疊成蛋白質。

Okay, let's recap.

好了，我們來回顧一下。

A gene is copied onto mRNA, which is then used to build proteins by assembling a chain of amino acids, aka transcription and translation.

基因被複制到 mRNA 上，然後通過組裝氨基酸鏈（又稱轉錄和翻譯）來構建蛋白質。

Welcome to Biology Pro Tips Season 2!

歡迎來到《生物學專業技巧》第二季！

If you want to decode a sequence of RNA, there is actually a chart for that.

如果你想解碼 RNA 序列，實際上有一個圖表可以實現。

Yeah, that's all.

對，就這樣

Have a great day.

祝你愉快

Oh yeah, did I mention that you have like a bunch of DNA?

對了，我有沒有說過你有一大堆 DNA？

You have about 20,000 protein-coding genes, each thousands to millions of bases long, and that only makes up around 1% of your entire DNA.

你有大約 2 萬個蛋白質編碼基因，每個基因都有數千到數百萬個鹼基長，而這隻佔你整個 DNA 的 1%左右。

The rest is just non-coding.

其餘的都是非編碼。

Plus, almost every cell in your body contains your entire genetic code, but certain genes can be turned on and off depending on the cell, which is good, because otherwise your brain cells might just start making stomach acid, which would not be good.

此外，你體內的幾乎每個細胞都包含你的全部遺傳密碼，但某些基因可以根據細胞的不同而開啟或關閉，這是件好事，否則你的腦細胞可能就會開始製造胃酸，那就不好了。

Fun fact!

有趣的事實

If you were to stretch out the DNA of just one single cell, it would be about two meters long.

如果把一個細胞的 DNA 拉長，長度大約為兩米。

Wait a minute, how does that fit into a microscopic cell?

等一下，這怎麼能裝進一個微型細胞呢？

Well, if you were to look inside the nucleus, you wouldn't find the DNA just floating around like this, or even this.

好吧，如果你觀察細胞核內部，你不會發現 DNA 就像這樣漂浮著，甚至是這樣。

No, you would actually find lots of these worm-looking things.

不，實際上你會發現很多這種蠕蟲模樣的東西。

To be exact, DNA is coiled up around proteins called histones, which are then condensed into strands of chromatin, which are then coiled up even more to make tightly packed units of DNA called chromosomes, which kind of look like worms.

確切地說，DNA盤繞在稱為組蛋白的蛋白質周圍，組蛋白凝結成染色質鏈，染色質鏈再盤繞成更緊密的DNA組織、部門，稱為染色體，看起來有點像蠕蟲。

Different sections on a chromosome carry different genes, and the entire human genome is split amongst 23 different chromosomes, although every body cell has two copies of every chromosome, one from the mother and one from the father.

染色體上的不同部分攜帶不同的基因，人類的整個基因組由 23 條不同的染色體組成，但每個體細胞的每條染色體都有兩個拷貝，一條來自母親，一條來自父親。

For most chromosomes, the two copies are said to be homologous, meaning that they carry the same genes in the same locations.

對於大多數染色體來說，兩個拷貝是同源的，這意味著它們在相同的位置攜帶相同的基因。

However, the two versions of a gene can be different, so the mother's gene could code for brown eyes, while the father's gene codes for blue eyes.

然而，一個基因的兩個版本可能是不同的，是以母親的基因可能編碼棕色眼睛，而父親的基因編碼藍色眼睛。

These different versions of a gene are called alleles.

這些基因的不同版本被稱為等位基因。

For most of your genes, you have two alleles, one on each chromosome from either parent.

對於大多數基因來說，你都有兩個等位基因，父母雙方的每條染色體上都有一個。

These alleles can be dominant or recessive, which determines which of them is expressed.

這些等位基因可以是顯性的，也可以是隱性的，這決定了其中哪一個等位基因會表達出來。

For example, brown eye color is a dominant trait, which is shown by an uppercase B, whereas blue is recessive, which is shown by a lowercase b.

例如，棕色眼睛是顯性性狀，用大寫字母 B 表示，而藍色是隱性性狀，用小寫字母 b 表示。

All this means is that if you have the dominant brown allele, you will have brown eyes, no matter what the second allele is.

這就意味著，如果你擁有顯性棕色等位基因，那麼無論第二等位基因是什麼，你的眼睛都會是棕色的。

Only when there are two recessive alleles will it be expressed.

只有當存在兩個隱性等位基因時，它才會表現出來。

With this knowledge, we can predict the future.

有了這些知識，我們就能預測未來。

Let's look at how this trait is inherited from parents to children.

讓我們看看這種特性是如何從父母遺傳給孩子的。

Both of these parents have brown eyes, but also have a recessive blue allele in their genotype.

這對父母的眼睛都是棕色的，但他們的基因型中也有一個隱性的藍色等位基因。

Every child receives one allele from each parent randomly, so these are the possible combinations for the children.

每個孩子都會從父母雙方隨機獲得一個等位基因，是以這些就是孩子們的可能組合。

Most combinations contain the dominant brown allele, so the child will have brown eyes.

大多數組合都含有顯性棕色等位基因，是以孩子的眼睛會是棕色的。

But there is a small chance that a child gets two recessive alleles and has blue eyes, even though both parents had brown eyes.

但是，即使父母的眼睛都是棕色的，孩子得到兩個隱性等位基因並擁有藍色眼睛的機率也很小。

You see, it's what's on the inside that counts.

你看，內在的東西才是最重要的。

Alright, that's cool, but reality is not always so simple.

好吧，這很酷，但現實並不總是那麼簡單。

Some genes are not fully dominant, but not fully recessive either, which means that the phenotype, so the appearance, appears to mix.

有些基因不是完全顯性的，但也不是完全隱性的，這意味著表型，即外觀，似乎是混合的。

Crossing a red and a white snapdragon, where red is dominant and white is recessive, gives you a pink phenotype, which is somewhere in between, a.k.a. intermediate inheritance.

將紅色和白色的金魚草雜交，紅色是顯性遺傳，白色是隱性遺傳，得到的表型是粉紅色，介於兩者之間，也就是中間遺傳。

Or, crossing a brown and a white cow, where both colors are dominant, could give you a spotted cow, so both phenotypes are expressed equally, a.k.a. codominance.

或者，將一頭棕色奶牛和一頭白色奶牛雜交，兩種顏色都是顯性，這樣就能得到一頭花斑奶牛，是以兩種表型表達相同，也就是共顯性。

Hey, remember how I said that almost all chromosomes are homologous?

嘿，還記得我說過幾乎所有的染色體都是同源的嗎？

Well, there's one exception, the sex chromosomes.

但有一個例外，那就是性染色體。

Females have two big X chromosomes, whereas males have one X and one smaller Y chromosome.

女性有兩條大的 X 染色體，而男性有一條 X 染色體和一條較小的 Y 染色體。

These are partially homologous at the top, but since the Y chromosome is so small, it's missing genes that are present on the lower part of the X chromosome.

這些基因在頂端部分是同源的，但由於 Y 染色體太小，所以缺少了 X 染色體下部的基因。

These genes are called X-linked genes.

這些基因被稱為 X 連鎖基因。

If one of these genes is a recessive trait, like colorblindness, males are stuck with that trait, whereas females probably have another dominant allele to override it.

如果這些基因中有一個是隱性性狀，比如色盲，那麼雄性基因就會有這種性狀，而雌性基因可能有另一個顯性等位基因來覆蓋它。

This is why most colorblind people are male.

這就是為什麼大多數色盲都是男性的原因。

Now, for genes to even be passed on, the body has to make new cells which can inherit the genes.

現在，要想讓基因遺傳下去，人體必須製造出能繼承基因的新細胞。

There's two main mechanisms.

主要有兩種機制。

Mitosis, which is how the body makes identical copies of body cells to grow in our pair of tissues, and meiosis, which is how the body makes gametes, so sperm and egg cells.

有絲分裂和減數分裂是人體制造配子（即精子和卵細胞）的方式。

Mitosis starts with a diploid cell, so a cell with two sets of chromosomes.

有絲分裂是從二倍體細胞開始的，即一個細胞有兩組染色體。

These chromosomes consist of one chromatid, which has to be replicated for the new cell.

這些染色體由一條染色單體組成，必須複製到新細胞中。

After replication is when you see the familiar X shape consisting of two identical sister chromatids.

複製後，您會看到由兩條相同的姐妹染色單體組成的熟悉的 "X "形狀。

These are split into two identical diploid cells with two sets of chromosomes consisting of one chromatid.

這些細胞分裂成兩個完全相同的二倍體細胞，其中有兩套由一條染色體組成的染色體。

Meiosis also starts with a diploid cell, but after replication, the chromosomes co-mingle and exchange genetic information in a process called crossing over.

減數分裂也是從一個二倍體細胞開始的，但在複製之後，染色體會在一個叫做交叉互換的過程中共同混合並交換遺傳信息。

The cells then split into two non-identical haploid cells.

然後，細胞分裂成兩個非相同的單倍體細胞。

These have one set of chromosomes, but they still consist of two sister chromatids.

它們只有一組染色體，但仍由兩條姐妹染色單體組成。

These cells split again into four genetically different haploid cells, where each chromosome has one chromatid.

這些細胞再次分裂成四個基因不同的單倍體細胞，每個染色體有一條染色單體。

Meiosis produces haploid cells so that when two gametes combine into a fertilized egg or zygote, it again has the correct number of chromosomes.

減數分裂產生單倍體細胞，是以當兩個配子結合成受精卵或合子時，它的染色體數目也是正確的。

This is cool, but cell division is only a tiny part of a cell's entire life cycle.

這很酷，但細胞分裂只是細胞整個生命週期的一小部分。

Most of its time is actually spent in interphase, aka just chilling.

實際上，它的大部分時間都是在間歇期度過的，也就是寒冷期。

All it does here is grow and replicate all of its DNA so that it actually has enough genetic material and size to divide in M phase.

它在這裡所做的一切就是生長和複製其所有 DNA，使其真正擁有足夠的遺傳物質和大小，以便在 M 階段進行分裂。

There's multiple checkpoints in the cell cycle which are controlled by proteins like p53 or cyclin to check if the cell is healthy and ready to reproduce.

細胞週期中有多個檢查點，由 p53 或細胞週期蛋白等蛋白質控制，檢查細胞是否健康，是否準備好進行繁殖。

If a cell is not quite right, it's either fixed or it destroys itself, which is called apoptosis.

如果細胞出現問題，要麼被固定，要麼自我毀滅，這就是所謂的細胞凋亡。

Or at least, that's what it should do.

至少，它應該這樣做。

Normal cells replicate until there's no need to, but some cells just keep going.

正常細胞一直在複製，直到沒有必要為止，但有些細胞卻一直在複製。

This is because they don't respond correctly to these checkpoints and end up replicating out of control and functioning wrong, which is also known as cancer.

這是因為它們沒有對這些檢查點做出正確反應，最終導致複製失控和功能錯誤，也就是所謂的癌症。