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?572Please respect copyright.PENANASTUEnpZG8A
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答案是,不會。572Please respect copyright.PENANAt83oZHreST
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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。572Please respect copyright.PENANAMnI9uA3p9E
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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。572Please respect copyright.PENANA3GNxSrPMHc
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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。572Please respect copyright.PENANAaaXd3DRSjc
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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。572Please respect copyright.PENANAUDu4k8OUH1
然而,當幹細胞變成正常細胞後,Telomerase的功能便會消失。572Please respect copyright.PENANAgO8CUB9N5H
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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。572Please respect copyright.PENANAIxiQmZGQSh
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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。572Please respect copyright.PENANA7ZsXQ6qd2y
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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?572Please respect copyright.PENANA2UYTeCcQS3
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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。572Please respect copyright.PENANAna0uAr2GY4
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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。572Please respect copyright.PENANAX0UWNrqHpX
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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。572Please respect copyright.PENANA4XqX0gO7gt
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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?572Please respect copyright.PENANAblY1uSQDTW
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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。572Please respect copyright.PENANA30baj3VLxu
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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;572Please respect copyright.PENANAS5R2cGcS8c
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。572Please respect copyright.PENANAbgzPnBUBFb
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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。572Please respect copyright.PENANAcJYvVchYDF
而老鼠每年會減少7000單位Telomere長度,最高壽命為5歲。572Please respect copyright.PENANAvcm1kz3iKV
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人類:每年減少71;120歲572Please respect copyright.PENANAQO6X15s3Qg
大象:每年減少109;66歲572Please respect copyright.PENANAikWbbBF2Tk
紅鸛:每年減少105;60歲572Please respect copyright.PENANAdPeO84wdEi
海豚:每年減少766;52歲572Please respect copyright.PENANAzqP3eRYn50
兀鷲:每年減少209;41歲572Please respect copyright.PENANALhsXYOCi2X
海鷗:每年減少771;25歲572Please respect copyright.PENANA4Vzp6DHpky
馴鹿:每年減少531;22歲572Please respect copyright.PENANAipsihRkF4u
山羊:每年減少363;21歲572Please respect copyright.PENANAfNJpBGhyEM
老鼠:每年減少7000;5歲572Please respect copyright.PENANAIG4L6QIOSe
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龜又是每年減少幾多呢?有待有心人發掘。572Please respect copyright.PENANAByK0pK53QM
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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。572Please respect copyright.PENANA5CgHhUA1R8
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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/toc572Please respect copyright.PENANAK297Pjqe7I
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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。572Please respect copyright.PENANAQ64GQ0GS9V
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Link:572Please respect copyright.PENANAGlnQMo7YTH
https://www.penana.com/user/27349/%E8%96%AF%E4%BB%94%E8%81%9E%E8%8C%B1%E8%8E%89/portfolio572Please respect copyright.PENANAnHbifNFX48
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有興趣接收科學資訊的話,歡迎follow IG: potatopigtongue。572Please respect copyright.PENANAZVYeO6PIZe
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Ref1:https://www.pnas.org/content/116/30/15122572Please respect copyright.PENANAUbQoEQFd7d