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？773Please respect copyright.ＰＥＮＡＮＡtk7yzXO3GC
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答案是，不會。773Please respect copyright.ＰＥＮＡＮＡtDzBL8UC83
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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。773Please respect copyright.ＰＥＮＡＮＡAz7SEpwooJ
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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。773Please respect copyright.ＰＥＮＡＮＡIfbk1nWIbo
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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。773Please respect copyright.ＰＥＮＡＮＡKvZNxk6R8h
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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。773Please respect copyright.ＰＥＮＡＮＡdHNvgcAky6
然而，當幹細胞變成正常細胞後，Telomerase的功能便會消失。773Please respect copyright.ＰＥＮＡＮＡKHbD5jCD3k
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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。773Please respect copyright.ＰＥＮＡＮＡcFZysHx94x
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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。773Please respect copyright.ＰＥＮＡＮＡuwv8kw5sAj
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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？773Please respect copyright.ＰＥＮＡＮＡsPqMi42Cvl
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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。773Please respect copyright.ＰＥＮＡＮＡSsBurebFkY
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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。773Please respect copyright.ＰＥＮＡＮＡgFElh6iby8
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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。773Please respect copyright.ＰＥＮＡＮＡNi39Z9ejTa
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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？773Please respect copyright.ＰＥＮＡＮＡpeH7NhSSKU
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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。773Please respect copyright.ＰＥＮＡＮＡcn1kxqSqGI
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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；773Please respect copyright.ＰＥＮＡＮＡc10RhLV2qg
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。773Please respect copyright.ＰＥＮＡＮＡZDNL1XUU23
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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。773Please respect copyright.ＰＥＮＡＮＡdwgSxjfcXk
而老鼠每年會減少7000單位Telomere長度，最高壽命為5歲。773Please respect copyright.ＰＥＮＡＮＡt77T6Bq09L
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人類：每年減少71；120歲773Please respect copyright.ＰＥＮＡＮＡY0WQLPJtd4
大象：每年減少109；66歲773Please respect copyright.ＰＥＮＡＮＡ3lUYjg8FXY
紅鸛：每年減少105；60歲773Please respect copyright.ＰＥＮＡＮＡ8sTJhgaOCo
海豚：每年減少766；52歲773Please respect copyright.ＰＥＮＡＮＡRWxY7dwCAV
兀鷲：每年減少209；41歲773Please respect copyright.ＰＥＮＡＮＡ83zkjJYskh
海鷗：每年減少771；25歲773Please respect copyright.ＰＥＮＡＮＡtOHdi0Wl0L
馴鹿：每年減少531；22歲773Please respect copyright.ＰＥＮＡＮＡA3zd5c7Z8X
山羊：每年減少363；21歲773Please respect copyright.ＰＥＮＡＮＡtRSYnKLrko
老鼠：每年減少7000；5歲773Please respect copyright.ＰＥＮＡＮＡA0M1VKBUzT
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龜又是每年減少幾多呢？有待有心人發掘。773Please respect copyright.ＰＥＮＡＮＡlJsBsa1uvr
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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。773Please respect copyright.ＰＥＮＡＮＡoGrllFyoQn
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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/toc773Please respect copyright.ＰＥＮＡＮＡ7Gu5gkhX04
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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。773Please respect copyright.ＰＥＮＡＮＡlzwTVpml5o
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Link:773Please respect copyright.ＰＥＮＡＮＡ39es4eS8LM
https://www.penana.com/user/27349/%E8%96%AF%E4%BB%94%E8%81%9E%E8%8C%B1%E8%8E%89/portfolio773Please respect copyright.ＰＥＮＡＮＡBk8a8OpAW6
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有興趣接收科學資訊的話，歡迎follow IG: potatopigtongue。773Please respect copyright.ＰＥＮＡＮＡSzis5lcO95
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Ref1:https://www.pnas.org/content/116/30/15122773Please respect copyright.ＰＥＮＡＮＡSzaMSVMw8o
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