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衰老的科学

The Science of Aging

虽然许多人寻找青春的源泉,但你可能首先想知道
While many search for the proverbial fountain of youth, you might be wondering
为什么我们会变老?是什么让我们的身体或细胞变老?
why do we age in the first place? What is it about our bodies or cells
有多种内部因素和外部因素如饮食,
biologically that causes us to grow old? There is a variety of internal and
锻炼或者环境压力
external factors such as diet, exercise or environmental stress which all
这些都会导致细胞损伤和修复,影响了变老的进度
contribute to cell damage and repair and effect the rate of aging, But the
然而令人吃惊的真相并不只这些,在基因组成中
surprising truth is that apart from these, we actually have a biological
我们确实有一个生物钟。这个钟表只能运行一定的时间
clock buried within our genetic makeup. And this clock can only run for so long,
换句话说,我们就像是被设定为走向死亡的程序,你的身体是由数以亿计的细胞组成
in other words we are programmed to die. Your body is made up of trillions of cells
他们不断分裂,伴随着每次分裂
which are constantly going through cell division and every time they divide they
他们也复制遗传物质DNA。DNA被组成一定的结构
make a copy of their DNA as well. This DNA is tightly packed into structures
成为染色体
called chromosomes
人类有23对染色体。问题就是DNA的复制
of which humans have twenty three pairs. The problem is, DNA replication isn’t
并不是那么完美,可能跳过染色体最后面的序列。
quite perfect and skips over the end of each chromosome.
为了保护重要的DNA不被切断
To protect against important DNA information being cut out we have
在我们承受范围内流失的染色体终端是位于染色体末尾的
something called telomeres on the end of chromosomes which are essentially
DNA重要的无意识复制。
meaningless repeats of DNA that we can afford to lose. But everytime
但是每次我们的染色体分裂,染色体终端变得越来越短
our cells divide these telomeres become shorter and shorter until eventually
直到最终它们彼此完全分离。在这时,细胞就不再分裂了。
they’ve been entirely stripped away. At which point the cell no longer divides.
有一些平状蠕虫可以无限再生染色体终端
Some flat worms are able to endlessly regenerate their telomeres making them
来实现高效的生物繁衍,但是它们的寿命不等
effectively biologically immortal, but their lifespans do vary and they’re
而且易感染疾病。所以说,
still susceptible to disease. Further suggesting that aging is a mix of
老化是受到基因和环境等因素的综合作用。
genetic and environmental factors.
但是为什么我们人类的细胞不是这样的呢?基本上来说,这种复制限制
But why don’t our cells do this? Ultimately this replication limit
实际有利于抵御癌症这种无限生长复制的细胞
actually helps to prevent cancer which is the uncontrollable growth of cells
并且减少细胞的死亡。一个细胞停止复制的时候
and evasion of cell death. The point at which a cell stops replicating is
就是到达了我们所说的“细胞衰老”的阶段。
known as cellular senescence.
在人类身体中,细胞的复制再生能力最多能达到50次左右。一旦达到了这个数值,
In humans this replication limit is around fifty times. Once it is reached the cell
细胞就开始功能失调并死亡,导致老化有关的特征。
gradually begins to lose its function and die causing age-related
这也说明了为什么人的寿命是一个来自于父母的
characteristics. This also helps to explain why life expectancy is a
显著遗传特点。
strongly heritable trait from your parents, because you got your initial
因为你从他们那里遗传到最初的染色体终端长度。
telomere length from them.
如果你有任何问题亟待解决,请在评论中或Facebook、Twitter等社交网站中留言,
Got a burning question you want answered? Ask it in the comments, or on facebook and twitter,
并订阅每周科学视频。
and subscribe for more weekly science videos.

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