無病無痛，沒有任何交通或人為意外的話，人類是否會進入不死永生狀態呢？746Please respect copyright.ＰＥＮＡＮＡaHjhlMnvBb
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答案是，不會。746Please respect copyright.ＰＥＮＡＮＡUCb7Qa23AS
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箇中的原因，就是在於染色體亦即是DNA的運作機制之上。746Please respect copyright.ＰＥＮＡＮＡyMuQQGfY1E
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（圖1）正常人體細胞分裂的時候，染色體的長度會越來越短。746Please respect copyright.ＰＥＮＡＮＡgFpSdeEDJd
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（圖2）染色體的頂端區域，我們稱之為Telomere。正常細胞分裂後，Telomere的長度便會越來越短，所以導致染色體的總長度亦會有所減少。746Please respect copyright.ＰＥＮＡＮＡZzL0uLAFLc
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（圖3）而幹細胞進行分裂的時候，則會有著Telomerase的協助，導致Telomere的長度便並不會有所減少。746Please respect copyright.ＰＥＮＡＮＡ3pTmQcN8S0
然而，當幹細胞變成正常細胞後，Telomerase的功能便會消失。746Please respect copyright.ＰＥＮＡＮＡV9zl2CpPxB
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（圖4）當Telomere長度削減到一定程度的時候，細胞便會自行啟動機制滅亡，又或者陷入衰老(Senescence)狀態。746Please respect copyright.ＰＥＮＡＮＡeaqwPJRsQr
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細胞滅亡或衰老的話，器官的功能便會衰退，最後亦會支撐不住，無法正常運作，促成死亡。746Please respect copyright.ＰＥＮＡＮＡvwiqMTW4XN
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你可能會問，現在科技如此倡明，那麼我們只要學習幹細胞的那一套方式，動用外力重啟Telomerase功能，那不就能踏入永生嗎？746Please respect copyright.ＰＥＮＡＮＡmyvQfIAEo1
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這個思路並沒有錯，只不過代價就是會增加患癌的風險。746Please respect copyright.ＰＥＮＡＮＡ7fnh3ZOlZi
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事實上，不少癌細胞的特徵就是Telomere長度非常之短，但又有著一定水平的Telomerase功能穩定維持著Telomere的長度，逃避進入滅亡的命運。746Please respect copyright.ＰＥＮＡＮＡQw2aOSZoeC
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另一方面的想，如果細胞真的是踏入「永生」狀態的話，終有一天無可避免會累積各種的DNA變異，促成癌細胞的誕生。746Please respect copyright.ＰＥＮＡＮＡhro3K0XSKV
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（圖5）既然Telomere對細胞的壽命有著重要影響的話，那麼一些較為長壽的物種是否擁有較長的Telomere呢？746Please respect copyright.ＰＥＮＡＮＡIOZOdtq4oE
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科學家比較各物種的Telomere後（Ref1)，發現海豚的起始Telomere長度比人類高出6倍以上，但壽命長度始終是人類佔優。746Please respect copyright.ＰＥＮＡＮＡnyJ5TuRFos
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反而，決定物種壽命長度的其中一種因素，則是Telomere衰減的速度；746Please respect copyright.ＰＥＮＡＮＡr3L7KBhG7B
Telomere衰減的速度只是一個參考性的指標，並非絕對。物種的大小、新陳代謝機制的不同等等均會對壽命長度有著影響。746Please respect copyright.ＰＥＮＡＮＡEOX70DOINl
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人類每年約會減少71單位Telomere的長度，最高壽命為120歲。746Please respect copyright.ＰＥＮＡＮＡWGvr6tktPU
而老鼠每年會減少7000單位Telomere長度，最高壽命為5歲。746Please respect copyright.ＰＥＮＡＮＡkZHwImYtwr
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人類：每年減少71；120歲746Please respect copyright.ＰＥＮＡＮＡAQLLEd1UIk
大象：每年減少109；66歲746Please respect copyright.ＰＥＮＡＮＡF7V8MdVWx6
紅鸛：每年減少105；60歲746Please respect copyright.ＰＥＮＡＮＡQ3xzfD1zEi
海豚：每年減少766；52歲746Please respect copyright.ＰＥＮＡＮＡ9edBzRXZfe
兀鷲：每年減少209；41歲746Please respect copyright.ＰＥＮＡＮＡfzuRQWezb1
海鷗：每年減少771；25歲746Please respect copyright.ＰＥＮＡＮＡQgkBCuim4N
馴鹿：每年減少531；22歲746Please respect copyright.ＰＥＮＡＮＡ4mvGnWBCez
山羊：每年減少363；21歲746Please respect copyright.ＰＥＮＡＮＡmsomN79D3J
老鼠：每年減少7000；5歲746Please respect copyright.ＰＥＮＡＮＡRcQ8pcm8hO
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龜又是每年減少幾多呢？有待有心人發掘。746Please respect copyright.ＰＥＮＡＮＡTqN7cQcVFz
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如果想我快啲出文的話，請入去Penana網站科普專欄–薯不揀單俾一個like以及Bookmark，這對我非常之重要。746Please respect copyright.ＰＥＮＡＮＡD6a25x4oa8
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Link: https://www.penana.com/story/66244/%E7%A7%91%E6%99%AE%E5%B0%88%E6%AC%84-%E8%96%AF%E4%B8%8D%E6%8F%80%E5%96%AE/toc746Please respect copyright.ＰＥＮＡＮＡZS4CHGILPj
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同時亦可以在Penana網站裡按「買一嚿/半嚿薯仔」，以課金的方式推動我繼續搜羅資料寫文，多謝。746Please respect copyright.ＰＥＮＡＮＡpYF85qbtuZ
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Link:746Please respect copyright.ＰＥＮＡＮＡu3d1dILo7p
https://www.penana.com/user/27349/%E8%96%AF%E4%BB%94%E8%81%9E%E8%8C%B1%E8%8E%89/portfolio746Please respect copyright.ＰＥＮＡＮＡGYebOXz35e
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有興趣接收科學資訊的話，歡迎follow IG: potatopigtongue。746Please respect copyright.ＰＥＮＡＮＡnCo5If8Bb5
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Ref1:https://www.pnas.org/content/116/30/15122746Please respect copyright.ＰＥＮＡＮＡIcSmsNZHzt
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