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  • Inside our cells, each of us has a second set of genes

    譯者: Lilian Chiu 審譯者: Amanda Zhu

  • completely separate from the 23 pairs of chromosomes

    我們每個人的細胞中, 都還有第二組基因,

  • we inherit from our parents.

    不包括在我們從父母遺傳 得到的二十三對染色體之內。

  • And this isn't just the case for humans

    且不只有人類是如此,

  • it's true of every animal, plant, and fungus,

    所有的動物、植物、真菌類,

  • and nearly every multicellular organism on Earth.

    以及地球上幾乎 所有的多細胞有機體也一樣。

  • This second genome belongs to our mitochondria,

    這第二組基因位在粒線體內,

  • an organelle inside our cells.

    粒線體是細胞中的一種胞器。

  • They're not fully a part of us, but they're not separate either

    它們不完全是我們的一部分, 也不完全不是。

  • so why are they so different from anything else in our bodies?

    它們為什麼會如此不同於 我們體內的所有其他東西?

  • Approximately 1.5 billion years ago,

    大約十五億年前,

  • scientists think a single-celled organism engulfed the mitochondria's ancestor,

    科學家認為,一種單細胞有機體

  • creating the predecessor of all multicellular organisms.

    吞噬了粒線體的祖先,

  • Mitochondria play an essential role:

    創造出了所有多細胞有機體的前身。

  • they convert energy from the food we eat and oxygen we breathe

    粒線體扮演了重要的角色:

  • into a form of energy our cells can use, which is a molecule called ATP.

    我們吃的食物和吸的氧氣中的能量

  • Without this energy, our cells start to die.

    就要靠它們轉換成 細胞可以運用的能量形式,

  • Humans have over 200 types of cells,

    即一種叫做三磷酸腺苷 ——即 ATP——的分子。

  • and all except mature red blood cells have mitochondria.

    沒有這種能量,細胞就會開始死亡。

  • That's because a red blood cell's job is to transport oxygen,

    人類的細胞類型超過兩百種,

  • which mitochondria would use up before it could reach its destination.

    除了成熟的紅血球細胞之外,

  • So all mitochondria use oxygen and metabolites to create energy

    全部都有粒細體。

  • and have their own DNA,

    原因是紅血球細胞的 工作是在運送氧,

  • but mitochondrial DNA varies more across species than other DNA.

    如果有粒細體在, 就會在抵達目的地前就把氧用光。

  • In mammals, mitochondria usually have 37 genes.

    所以,所有的粒線體

  • In some plants, like cucumbers, mitochondria have up to 65 genes,

    都會用氧和代謝產物來創造能量,

  • and some fungal mitochondria have only 1.

    且擁有它們自己的 DNA,

  • A few microbes that live in oxygen-poor environments

    但粒線體 DNA 在不同物種間的差異性

  • seem to be on the way to losing their mitochondria entirely,

    比其他 DNA 更高。

  • and one group, oxymonad monocercomonoides, already has.

    哺乳類動物的粒線體 通常有三十七個基因。

  • This variety exists because mitochondria are still evolving,

    至於一些植物,如黃瓜,

  • both in tandem with the organisms that contain them,

    其粒線體有高達六十五個基因,

  • and separately, on their own timeline.

    有些真菌類的粒線體則只有一個基因。

  • To understand how that's possible,

    少數幾種生活在稀氧環境中的微生物

  • it helps to take a closer look at what the mitochondria inside us are doing,

    幾乎快完全失去粒線體,

  • starting from the moment we're conceived.

    而有一類屬於類單鞭滴蟲屬的微生物,

  • In almost all species, mitochondrial DNA is passed down from only one parent.

    已經沒有粒線體了。

  • In humans and most animals, that parent is the mother.

    會有這樣的多樣性,

  • Sperm contain approximately 50 to 75 mitochondria in the tail,

    是因為粒線體仍然在演化,

  • to help them swim.

    包括與它們所屬的有機體一起演化,

  • These dissolve with the tail after conception.

    以及依它們自己的時間表單獨演化。

  • Meanwhile, an egg contains thousands of mitochondria,

    要了解怎麼可能會如此,

  • each containing multiple copies of the mitochondrial DNA.

    可以先細究粒線體 在我們體內做些什麼,

  • This translates to over 150,000 copies of mitochondrial DNA

    從懷孕的那一刻開始談起。

  • that we inherit from our mothers,

    幾乎所有物種的粒線體 DNA

  • each of which is independent and could vary slightly from the others.

    都是由父母其中之一所傳下來。

  • As a fertilized egg grows and divides,

    就人類和大部分動物而言,是母親。

  • those thousands of mitochondria are divvied up into the cells

    精子尾部含有大約 五十到七十五個粒線體,

  • of the developing embryo.

    用以協助它們游泳。

  • By the time we have differentiated tissues and organs,

    受孕之後,這些粒線體 就會和尾部一起溶解。

  • variations in the mitochondrial DNA are scattered at random throughout our bodies.

    一個卵子則含有數千個粒線體,

  • To make matters even more complex,

    每個都含有多個粒線體 DNA。

  • mitochondria have a separate replication process from our cells.

    算起來就有超過十五萬個粒線體 DNA

  • So as our cells replicate by dividing, mitochondria end up in new cells,

    都是來自我們的母親,

  • and all the while they're fusing and dividing themselves,

    每個粒線體都是獨立的, 且可能互相都有些微不同。

  • on their own timeline.

    隨著受精卵成長和分裂,

  • As mitochondria combine and separate,

    那數千個粒線體會分裂並分配到 發展中胚胎的各細胞當中,

  • they sequester faulty DNA or mitochondria that aren't working properly for removal.

    當細胞已分化出組織和器官之後,

  • All this means that the random selection of your mother's mitochondrial DNA

    粒線體 DNA 的差異

  • you inherit at birth

    就會隨機散佈到我們全身各處。

  • can change throughout your life and throughout your body.

    更複雜的是,

  • So mitochondria are dynamic and, to a degree, independent,

    粒線體和細胞的複製過程是分開的。

  • but they're also shaped by their environments: us.

    所以,當細胞透過分裂來複製時,

  • We think that long ago,

    粒線體就會進入到新的細胞中,

  • some of their genes were transferred to their host's genomes.

    而在此過程中,粒線體 也一直依循著自己的時間表

  • So today, although mitochondria have their own genome

    進行融合和分裂。

  • and replicate separately from the cells that contain them,

    隨著粒線體結合和分離,

  • they can't do this without instruction from our DNA.

    它們會把有缺陷、無法妥當運作的 DNA 或粒線體隔離並除去。

  • And though mitochondrial DNA is inherited from one parent,

    也就是說,你在出生時 從母親身上隨機選擇

  • the genes involved in building and regulating the mitochondria

    而繼承的粒線體 DNA,

  • come from both.

    在你一生中、在你體內各處 都有可能會改變。

  • Mitochondria continue to defy tidy classification.

    所以粒線體會不斷變化, 某種程度上也是獨立的,

  • Their story is still unfolding inside of each of our cells,

    但它們的環境,即我們, 也會改變它們。

  • simultaneously separate and inseparable from our own.

    我們認為,很久以前,

  • Learning more about them can both give us tools

    它們的一些基因 被轉移給其宿主的基因組。

  • to protect human health in the future, and teach us more about our history.

    所以現今雖然粒線體 有它們自己的基因組,

Inside our cells, each of us has a second set of genes

譯者: Lilian Chiu 審譯者: Amanda Zhu

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B2 中高級 中文 美國腔 TED-Ed 粒線體 細胞 基因 分裂 複製

The genes you don't get from your parents (but can't live without) - Devin Shuman

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    nao 發佈於 2021 年 10 月 06 日
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