cell death

[Mike Onken]

"Austin So (Hae Jin)" wrote:

> LJ Smith wrote:
>
> > Assuming that cells are "programmed" to undergo a certain number of divisions
> > and then they die, how is it that we have a continuous amount of cells to
> > replace the dead ones, such as with skin cells?  Where do these "fresh" cells
> > come from?
>
> Cells are believed to be able to undergo 40-50 rounds of mitosis...

???  Where did that number come from???

Basal Keratinocytes undergo mitosis once every day or two.  So on average, assuming a
human lifetime around 70 years, skin cells undergo 25,000 rounds of mitosis.  The
same is true of epithelial cells throughout the body.  The problem of telomere
shortening only appears when these cells are cultured away from their native stroma.


--
Michael Onken   -. .-.   .-. .-.   . mdonken at artsci.wustl.edu
Mol. Cell Biol. ||X|||\ /|||X|||\ /| URL:
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