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？790Please respect copyright.ＰＥＮＡＮＡGvFSbucoRq
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答案是，不會。790Please respect copyright.ＰＥＮＡＮＡ6fY5m8Mu97
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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。790Please respect copyright.ＰＥＮＡＮＡmqajoe9kbP
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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。790Please respect copyright.ＰＥＮＡＮＡ2yC9sSwNby
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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。790Please respect copyright.ＰＥＮＡＮＡ35u87WmmR3
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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。790Please respect copyright.ＰＥＮＡＮＡ5ouQwJeCJl
然而，當幹細胞變成正常細胞後，Telomerase的功能便會消失。790Please respect copyright.ＰＥＮＡＮＡs3K5COLrLY
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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。790Please respect copyright.ＰＥＮＡＮＡrnkmP9QMKA
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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。790Please respect copyright.ＰＥＮＡＮＡ9QqyA3O7zR
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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？790Please respect copyright.ＰＥＮＡＮＡBqQ5NzG6pi
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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。790Please respect copyright.ＰＥＮＡＮＡuMzqA3qkMs
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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。790Please respect copyright.ＰＥＮＡＮＡRLk2CWZx0G
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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。790Please respect copyright.ＰＥＮＡＮＡ7wPrnDNPn3
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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？790Please respect copyright.ＰＥＮＡＮＡhJ8jXSw46D
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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。790Please respect copyright.ＰＥＮＡＮＡexSEb1LC7o
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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；790Please respect copyright.ＰＥＮＡＮＡe3e5rsxnJ0
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。790Please respect copyright.ＰＥＮＡＮＡqscsV0JDbT
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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。790Please respect copyright.ＰＥＮＡＮＡXbyCxtZ4n9
而老鼠每年會減少7000單位Telomere長度，最高壽命為5歲。790Please respect copyright.ＰＥＮＡＮＡxqdLOyLUKk
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人類：每年減少71；120歲790Please respect copyright.ＰＥＮＡＮＡH9qv8LfmDs
大象：每年減少109；66歲790Please respect copyright.ＰＥＮＡＮＡbaOwn15Jyq
紅鸛：每年減少105；60歲790Please respect copyright.ＰＥＮＡＮＡjwFIAcOSBf
海豚：每年減少766；52歲790Please respect copyright.ＰＥＮＡＮＡtumuZnsNaf
兀鷲：每年減少209；41歲790Please respect copyright.ＰＥＮＡＮＡ6Fv0zUdqCW
海鷗：每年減少771；25歲790Please respect copyright.ＰＥＮＡＮＡUIq7zpvMGK
馴鹿：每年減少531；22歲790Please respect copyright.ＰＥＮＡＮＡiHfhVUp53A
山羊：每年減少363；21歲790Please respect copyright.ＰＥＮＡＮＡokWhmeMcwk
老鼠：每年減少7000；5歲790Please respect copyright.ＰＥＮＡＮＡkai119Ev3F
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龜又是每年減少幾多呢？有待有心人發掘。790Please respect copyright.ＰＥＮＡＮＡ3ugrLBCU5G
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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。790Please respect copyright.ＰＥＮＡＮＡbmCZ9JLvFD
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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/toc790Please respect copyright.ＰＥＮＡＮＡj9Zy9j5vAB
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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。790Please respect copyright.ＰＥＮＡＮＡKh0ENE43cV
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Link:790Please respect copyright.ＰＥＮＡＮＡoOQS3YHxiT
https://www.penana.com/user/27349/%E8%96%AF%E4%BB%94%E8%81%9E%E8%8C%B1%E8%8E%89/portfolio790Please respect copyright.ＰＥＮＡＮＡalBCgghzs6
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有興趣接收科學資訊的話，歡迎follow IG: potatopigtongue。790Please respect copyright.ＰＥＮＡＮＡ7UfKjmFjLA
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Ref1:https://www.pnas.org/content/116/30/15122790Please respect copyright.ＰＥＮＡＮＡgqSp2u6EIp
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