telomeres

Malcolm McMahon cuhes at csv.warwick.ac.uk
Thu Jun 2 04:53:17 EST 1994


In article <68388 at sdcc12.ucsd.edu>,
	wsun at jeeves.ucsd.edu (Fiberman) writes:
>In article <2s2c6h$hj1 at crocus.csv.warwick.ac.uk> cuhes at csv.warwick.ac.uk (Malcolm McMahon) writes:
>
>>The death clock argument is the first suggested mechanism of aging that
>>has ever made sense to me because it explains why there are no imortal
>>mutants - they die of cancer before we notice they are immortal.
>
>But using the same argument as above.  There must be a way to
>prevent cancer in old age.  A single cell can develop into an
>organism without any problems, why would an adult organism
>eventually develop cancer?
>

The death clock _is_ such a protective mechanism. It presents a second
hurdle that a mutation must overcome to be a "successful" cancer. This is
because a cancer that does no overcome the death clock will quickly use up
its alloted number of divisions. A single cell does not always make it to
an adult organism. I think that, approximately, any given cell has a 
certain chance of becoming cancerous in a given time regardless of age etc.

If you take the rough approximation that, with the ageing clock, the mutation
has to overcome two successive obstacles to become a maligancy: the ordinary
controls and the death clock and guess that the chances of overcoming each
are about the same then, were the death clock stopped, the odds against
you getting a malignancy in any time period would presumably be reduced
to the square root. Supposing (another guesstimate) the chances of contracting
a malignancy in any year are 200 to 1 against then removing the death clock
would make them 14 to 1. If this is even approximately true it's no wonder
we don't see imortal mutants.

Malcolm




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