While many search for the proverbial
fountain of youth, you might be wondering why do we age in the first place?
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 environmental stress which all contribute to cell damage and repair and
effect the rate of aging, But the surprising truth is that apart from these, we actually have a biological clock buried within 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. 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 everytime our cells divide these telomeres become
shorter and shorter until eventually they’ve been entirely stripped away. At
which point the cell no longer divides. Some flat worms are able to endlessly
regenerate their telomeres making them effectively biologically immortal, but
their lifespans do vary and they’re still susceptible to disease further
suggesting that aging is a mix of genetic and environmental factors. 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. Got a burning question you want answered?
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