while many search for the proverbial fountain of youth, you might be wondering why do we age in the first place? 關於眾所皆知的年輕的泉源雖然有很多研究，你可能壓根還是想知道我們為什麼會變老 (proverbial硬插進去顯得多餘，不知道要不要直接省略) What is it about our bodies or cells biologically that causes us to grow old? There is a variety of internal and external factors such as diet, exercise or environment stress which all contribute to cell damage and repair and effect the rate of aging. 生物學上，是有關身體和細胞的什麼讓我們變老? 有許多不同的內外因素像是飲食，運動或是環境的壓力都會造成細胞的傷害和修復且影響 老化的速率。 (第一句很不確定是這樣翻) But the suprising truth is that apart from these, we actually have a biological clock buried with our genetic makeup. And this clock can only run for so long, in other words we are programmed to die. Your body is made up of trillions of cells which are constantly going through cell division and every time they divide they make a copy of their DNA as well. 但驚人的真相是除此之外，我們有個埋藏在基因構造的生理時鐘。這個時鐘可以運行很久 ，也就說我們是預定好要死的。你的身體由數兆個細胞組成，這些細胞不停的經歷細胞分 裂，且每次也產生自身DNA的複本。 (雖然我翻成"埋藏在基因構造的生理時鐘"，不過應該是要buried in吧? 但我又不覺得它的意思是"和基因構造一起被埋藏的生理時鐘"，不知道大家的看法如何? 還有"can only run for so long"中的only和so long加在一起不知道怎麼說，所以就不 翻only了...) This DNA is tightly packed into structures called chromosomes of which humans have twenty three pairs. The problem is, DNA replication isn't quite perfect and skips over the end of each chromosome. To protect against important DNA information being cut out, we have something called telomeres on the end of chromosomes which are essentially meaningless repeats of DNA that we can afford to lose. But every time our cells divide these telomeres become shorter and shoter until eventually they've been entirely stripped away. At which point the cell no longer divides. 這個DNA被緊密的包進叫做染色體的結構，而人類有23對染色體。問題是DNA的複製並不這 麼完美，它會略過每個染色體的尾端。為了保護重要的DNA資訊不被切斷，我們在染色體的 尾端有叫做端粒的東西，本質上是我們足以捨棄的無意義DNA連續片段。但隨著每次的分裂 這些端粒就愈來愈短，最後就完全的被除去。到了這個時候，細胞就不再分裂了。 Some flatworms are able to endlessly regenerate their telomeres making them effectively biologically immoral, but their lifespans do vary and they're still susceptible to disease further suggesting that aging is a mix of genetic and enviromental factors. 有些扁形動物可以無窮地產生自身的端粒，造成牠們實際上是幾乎不死的，但牠們的壽命 不一且還是會受疾病的侵襲，暗示了老化是基因和環境要素的組合。 But why don't our cells do this? Ultimately this replication limit actually helps to prevent cancer which is the uncontrollable growth of cells and evasion of cell death. The point at which a cell stops replicating is known as cellular senescence. In humans this replication limit is around fifty times. Once it is reached the cell gradually begins to lose its function and die causing age-related characteristics. This also helps to explain why life expectancy is a strongly heritable trait from your parents, because you got your initial telomere length from them. 但為什麼我們的細胞不這麼做呢?最終這種複製上的限制實際會幫助預防那些不受控制的 細胞成長和不會衰老的細胞所造成的癌症。此時細胞停止複製即為所謂的細胞衰老。 在人類中這種限制大約為50次，之後細胞便逐漸喪失牠的功能接著死亡，產生年老相關的 特徵。這也幫助解釋為什麼壽命和你的雙親有很大的繼承特性，因為你的初始端粒長度是 從他們來的。 (除了我翻譯提出的問題，如果有看到不妥的地方也麻煩糾正我，謝謝大家:D) --

※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 36.229.85.58 ※ 編輯: Minilogo 來自: 36.229.86.21 (03/24 14:20)