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?534Please respect copyright.PENANAAG7FDV7GdR
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答案是,不會。534Please respect copyright.PENANAUCMUxdle8m
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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。534Please respect copyright.PENANAb0xQK4SWCd
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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。534Please respect copyright.PENANAqXYWyVA1FL
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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。534Please respect copyright.PENANAApABrDkp5w
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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。534Please respect copyright.PENANA7nZu9XeNNB
然而,當幹細胞變成正常細胞後,Telomerase的功能便會消失。534Please respect copyright.PENANACOvJS0Ta02
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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。534Please respect copyright.PENANAkV3q2MaOt5
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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。534Please respect copyright.PENANA3gMXjluLql
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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?534Please respect copyright.PENANACY0CGZACr0
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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。534Please respect copyright.PENANA0KxoTA5pr4
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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。534Please respect copyright.PENANAm0EmYubCh5
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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。534Please respect copyright.PENANAJwvcCcQc0q
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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?534Please respect copyright.PENANAiZD3Cpdzpb
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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。534Please respect copyright.PENANA7PHavZVikm
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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;534Please respect copyright.PENANAn0UHAM3SVG
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。534Please respect copyright.PENANAYHGNVGcseG
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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。534Please respect copyright.PENANAD5QU2M6J5i
而老鼠每年會減少7000單位Telomere長度,最高壽命為5歲。534Please respect copyright.PENANAz9EmZLAnxo
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人類:每年減少71;120歲534Please respect copyright.PENANAA8kJLQVnkE
大象:每年減少109;66歲534Please respect copyright.PENANAqZgC9T4egS
紅鸛:每年減少105;60歲534Please respect copyright.PENANADWhLwgbPYI
海豚:每年減少766;52歲534Please respect copyright.PENANAqoYA0rtGqx
兀鷲:每年減少209;41歲534Please respect copyright.PENANAoZgUazWnoZ
海鷗:每年減少771;25歲534Please respect copyright.PENANAqfdpXBvFLL
馴鹿:每年減少531;22歲534Please respect copyright.PENANAm4OgBwkl6j
山羊:每年減少363;21歲534Please respect copyright.PENANABt3xoVmrXi
老鼠:每年減少7000;5歲534Please respect copyright.PENANAmad0gke9Yk
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龜又是每年減少幾多呢?有待有心人發掘。534Please respect copyright.PENANAgmLmdiNEb0
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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。534Please respect copyright.PENANA5r65QdBkPZ
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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/toc534Please respect copyright.PENANA6Mu7dMgLP5
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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。534Please respect copyright.PENANA5THx3ZBIzt
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Link:534Please respect copyright.PENANAcCJSTY6l2c
https://www.penana.com/user/27349/%E8%96%AF%E4%BB%94%E8%81%9E%E8%8C%B1%E8%8E%89/portfolio534Please respect copyright.PENANAQK0NpYeIwX
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有興趣接收科學資訊的話,歡迎follow IG: potatopigtongue。534Please respect copyright.PENANAMgZTewUxPG
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Ref1:https://www.pnas.org/content/116/30/15122534Please respect copyright.PENANAWKMNzcsrbf