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  • Thanks to Brilliant for supporting this whole week of SciShow.

    感謝 Brilliant 對 SciShow 本周的支持。

  • Go to Brilliant.org/SciShow to learn more.

    到 Brilliant.org/SciShow 了解更多資訊。

  • When you hear the wordscurvy,” you probably think of

    當你聽到「壞血症」時,你可能會想到

  • jokes about pirates, but this disease

    某些有關海盜的笑話,但這個疾病

  • can actually be really serious.

    其實非常嚴重。

  • Its symptoms include bleeding gums;

    其症狀包括牙齦出血

  • bumpy, rashy skin; and joint pain,

    皮膚粗糙、關節疼痛,

  • and if it's not treated, it can be deadly.

    而且如果不治療的話,可能會致命。

  • It's not just a thing of the past, either.

    這不只是以前的疾病。

  • Scurvy still shows up in developing nations,

    壞血症仍出現在發展中國家,

  • and dozens of cases were reported in

    而且在過去十年,

  • the United States in the last decade.

    美國就傳出數十例。

  • Thankfully, it is relatively easy to treat

    幸好,這種疾病相對好治療。

  • all you need is a high dose of Vitamin C.

    你只需要高劑量的維他命 C。

  • But here's the thing:

    但問題是:

  • If it weren't for a quirk of evolution,

    如果不是因為怪異的演化,

  • nobody would have ever gotten scurvy in the first place.

    一開始根本沒人會得壞血症。

  • The reason Vitamin C cures scurvy is because

    維他命C 可以治療壞血症的原因是,

  • the disease is actually caused by a Vitamin C deficiency.

    壞血症其實是由於缺乏維他命 C 所造成。

  • Without this vitamin, the body can't properly form collagen.

    沒有這種維他命,身體就無法正常形成膠原蛋白。

  • Collagen is the protein that makes up

    膠原蛋白是構成

  • the vast majority of our connective tissues,

    我們絕大多數結締組織的蛋白質,

  • so without enough of it, things can go seriously wrong.

    所以要是沒有足夠的膠原蛋白,身體就會變得很糟。

  • For example, scurvy patients can develop skin

    例如,壞血症患者的皮膚

  • that's thin and fragile, where any wounds they get

    會變得又薄又脆弱,得到的任何傷口

  • stay open and can't heal.

    都會變開放性且無法痊癒。

  • That can make them more likely to contract a life-threatening infection.

    這讓患者更有可能感染威脅生命的傳染病。

  • Scurvy can also cause the collagen supporting

    壞血症也會造成由膠原蛋白

  • blood vessels to fall apart, which can lead to hemorrhages.

    支撐的血管破裂,進而導致出血。

  • So this protein is a pretty big deal

    所以,這種蛋白質非常重要。

  • and by extension, so is Vitamin C.

    此外,維他命 C 當然也是。

  • To be clear, this vitamin isn't the only thing we need to make collagen.

    坦白說,這種維他命不是製作膠原蛋白的唯一物質。

  • But it is the only component of the collagen

    但它是膠原蛋白在合成過程中

  • synthesis process our bodies can't naturally produce.

    身體無法自然產生的成分。

  • We need to consume it somehow.

    我們需要以某種方式攝取。

  • That's why a lack of it leads to scurvy,

    這就是為什麼缺乏維他命 C 會導致壞血症,

  • and why a high dose of it can cure the disease.

    而且為什麼高劑量的維他命 C 可以治療壞血症。

  • But what's interesting is that most of nature doesn't have to deal with this.

    但有趣的是,自然界的大多數生物都不必應付這問題。

  • Lots of animals can make their own Vitamin C

    很多動物可以自己製造維他命 C,

  • without consuming it in their diets.

    而不需要從食物中攝取。

  • And here's the kicker:

    更重要的是:

  • Our very distant primate ancestors could do this, too.

    我們久遠的靈長類祖先也能這麼做。

  • More than 60 million years ago,

    在 6000 多萬年前,

  • the branch of primates that now includes humans

    靈長類的分支,包含現在的人類

  • did have the ability to make Vitamin C.

    確實有能力製作維他命 C。

  • But then we lost it.

    但我們後來失去這種能力。

  • More specifically, we lost the ability to make an enzyme called GULO.

    更具體來說,我們失去製作一種叫 GULO 酵素的能力

  • Just like with collagen, the process of making

    就像製作膠原蛋白一樣,製作

  • Vitamin C is... a process.

    維他命 C 的過程...是一個過程。

  • But for this story, all you need to know

    但在這裡,你要知道的是

  • is that the last step depends on GULO.

    最後一個步驟仰賴於 GULO。

  • When you look at different animals' genomes,

    你在看不同動物的基因組時,

  • you'll see that most animals have the gene that codes for this enzyme.

    你會發現大多動物都有編碼這種酵素的基因。

  • And those that do can tweak how much

    牠們可以調整

  • or how little Vitamin C they produce.

    維他命 C 產生的多寡。

  • Like, rabbits pump out way more GULO enzymes

    例如,在冬天,富含維他命 C 的食物

  • during the winter months when Vitamin C-rich foods

    供給短缺時,兔子會產生大量的 GULO 酵素。

  • are in short supply, and goats can really crank it out

    而山羊也會在生病或緊張時

  • when they're sick or stressed.

    製造這種酵素。

  • Even animals toward the bottom of the evolutionary tree,

    就算是在演化樹底層的那些動物,

  • like sponges and jellyfish, have the gene

    像是海綿和水母,也有產生

  • responsible for GULO, which means

    GULO 的基因,這代表

  • it's existed for a very long time.

    GULO 已經存在很久了。

  • The only members of the no-GULO club are

    無-GULO 俱樂部的成員只有

  • guinea pigs, some bats and birds, most fish...

    天竺鼠、某些蝙蝠、大多數的魚類...

  • and many primates, including humans.

    還有很多靈長類,包括人類。

  • So in our evolutionary past, our very distant ancestors

    所以在我們演化史上,我們的遠祖

  • had the ability to make GULO and therefore Vitamin C.

    都有能力製作 GULO 和維他命 C。

  • But somewhere in primate evolution, a random mutation broke it.

    但靈長類演化的某個時間點,有個隨機突變破壞了這能力。

  • This might seem more than a little unfair,

    這可能好像有點不公平,

  • but you have to remember, mutations are random.

    但你要記住,突變是隨機的。

  • Most of the time, they're harmless and unnoticeable,

    大多時候都無害且不明顯,

  • but sometimes they affect an important gene.

    但有時會影響重要的基因。

  • And when they dowell, it just kind of stinks.

    如果影響到...好吧,會有點遭。

  • We can tell this happened to GULO

    我們可以知道 GULO 發生的事。

  • because its gene is actually still in our genetic code

    因為它的基因其實仍在我們的遺傳編碼中。

  • although these days, it's just something called a pseudogene.

    雖然現在是叫作假基因。

  • That's a copy of a DNA sequence

    那是 DNA 序列的複製品。

  • that accumulated enough mutations that it can't

    它累積了足夠突變,導致無法

  • perform its original jobor in the case of the GULO gene,

    完成原本的工作,或是在 GULO 基因下,

  • accumulated enough that it's totally nonfunctional.

    累積足夠完全喪失功能的突變。

  • Pseudogenes actually crop up all the time,

    假基因其實一直都在,

  • and the GULO gene is one of about 20,000 others in our genome.

    而 GULO 基因是基因組中,其他 20,000 個基因中的一個。

  • For reference, we have about 27,000 genes

    我們有大約 27,000 個基因做為參考,

  • that actually make what they're supposed to.

    它們其實可以製造原本該製造的物質。

  • So, you knowour genomes are kind of a mess.

    所以說…我們的基因組有點亂。

  • But that's a little beside the point here.

    但這有點離題了。

  • The real question is, why did the nonfunctional

    真正的問題是,為何失去作用的

  • GULO gene get passed down in the first place?

    GULO 基因一開始會遺傳下來?

  • After all, we can literally die without Vitamin C.

    畢竟,我們沒有維他命 C 確實會死。

  • So it seems like the first primates to get this

    所以似乎第一批獲得這些

  • broken gene should have died before they could pass it along to their offspring.

    殘缺基因的靈長類,應該在遺傳給後代前死亡。

  • Well, scientists have looked into it,

    科學家已經研究過了

  • and they've come up with a hypothesis about what happened.

    而他們對此提出一個假設。

  • A part of it could be that there is some benefit to ditching the GULO gene.

    其中部分原因可以是,丟掉 GULO 基因可能有其他好處。

  • GULO can create hydrogen peroxide as a

    GULO 可以製造過氧化氫

  • byproduct of its reaction, which can form particles

    作為其反應的副產品,當過氧化氫分解時,

  • called free radicals when it breaks down.

    會形成叫自由基的分子。

  • These are little free-floating electrons

    這些微小、自由浮動的電子

  • that have the potential to harm cells

    可能會傷害細胞,

  • and make certain diseases more likely.

    讓某些疾病更可能產生。

  • So it seems helpful to produce as few of them as possible.

    所以盡可能減少產生它們,似乎對我們有好處。

  • But then againthat's a marginal benefit at best,

    但一樣… 這是考慮到沒有維他命 C 的情況,

  • considering what happens without Vitamin C.

    充其量只是邊際效益。

  • So the better explanation seems to be that

    比較好的解釋是,

  • the GULO pseudogene wasn't eliminated

    GULO 的假基因沒有受到清除,

  • because there just wasn't enough selective pressure.

    是因為進化壓力還不夠的關係。

  • Not making GULO is easy to compensate for

    如果是可以在飲食中大量攝取維生素 C 的動物,

  • if you're an animal that consumes plenty of Vitamin C in your diet.

    即使沒有製作 GULO 的能力也能得到補償。

  • And at the point in our ancestry where primates lost the GULO gene,

    在我們的祖先,靈長類失去 GULO 的基因時,

  • they lived mostly in tropical environments,

    他們主要生活在熱帶環境,

  • so their diets contained plenty of fruits and vegetables.

    因此他們的飲食中,含有大量的水果和蔬菜。

  • So we probably never noticed the ability to

    所以,我們大概沒注意到

  • synthesize this vitamin was gone because,

    這種合成維他命的能力失去了,因為

  • well, we got it pretty easily in our diets.

    嗯,我們可以輕鬆從飲食中獲得。

  • Today, that seems pretty rough,

    現在,情況還是很遭,

  • considering that scurvy is still a problem.

    因為壞血症仍是個問題。

  • But unfortunately, that's just how evolution plays out sometimes.

    但不幸的是,有時演化就是這樣。

  • The best we can do now is try and

    我們能做的就是努力

  • make sure everyone gets what they need.

    確保每個人能得到他們需要的。

  • Scurvy isn't anything to joke about,

    壞血症不是什麼玩笑話

  • but there are plenty of other great jokes you

    但你還能從故事書中的海盜

  • can make about storybook pirates.

    找到很多其他笑話。

  • Like, anything about booty is a good time.

    像是,任何戰利品都會讓人愉快。

  • Pirates are always collecting it, counting it,

    海盜總是收集、數數它們的數量,

  • and divvying it up among their crew.

    然後分給其他船員。

  • And if you want to experience some of that

    如果你想自己體驗一下,

  • for yourself, you can check out the Logic course from Brilliant.

    你可以在 Brilliant 那了解邏輯課程。

  • It features a quiz that's all about pirates,

    它是以海盜為特色的小測驗,

  • where you use your new logic skills to

    可以使用新的邏輯技巧,

  • figure out who's cheating whom out of the most booty.

    在大多數的戰利品中,找出誰在欺騙人。

  • It's a fun time, and Brilliant also has a bunch

    這很有趣,而且 Brilliant 還有其他

  • of other courses that can help you cultivate

    課程可以幫你培養

  • your math and scientific thinking skills.

    數學和科學的思維能力。

  • They're also available offline using

    Brilliants iOS 和 Android 的應用程式

  • Brilliants iOS and Android app.

    都可以離線使用。

  • So whether you're stuck on the subway

    所以不論你是在地下鐵坐車,

  • or sailing the seven seas, you'll be able to keep learning.

    還是航行於七海中,你都能持續學習。

  • If you're one of the first 200 people to sign up

    如果你是前 200 名

  • at Brilliant.org/SciShow, you'll also get 20% off an annual Premium subscription.

    在 Brilliant.org/SciShow 註冊的人,你也會得到年度高級訂閱的 20% 折扣。

  • And you'll be helping SciShow make more content, too!

    同時也是在幫 SciShow 製作更多內容!

Thanks to Brilliant for supporting this whole week of SciShow.

感謝 Brilliant 對 SciShow 本周的支持。

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B1 中級 中文 美國腔 維他命 基因 靈長類 酵素 製作 突變

為什麼壞血病不應該存在? (Why Scurvy Shouldn't Exist)

  • 237 10
    Jerry Liu 發佈於 2021 年 01 月 14 日
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