Why do we die

D.C.Jeffares at massey.ac.nz D.C.Jeffares at massey.ac.nz
Thu Nov 16 17:49:02 EST 1995

Another way to look at the why we die is to consider how long a cell line 
can last. Mammal cells in culture seem to last only a certain number of 
generations - an exception is tranformed (cancerous) cells, such as HeLa 
cells which appear to be immortal. Its interesting that plants differ 
here, in that plant meristem cells can continue to regerate entire 
indoividuals for very long periods of time, and can regenerate an entire 
organism in favourable culture conditions.

It has long been known that telomeres (the specialsed end bits of 
chromosomes) shorten through the lifetime of vertebrate tissue, apart 
from cencer cells in culture. So that our chromosomes just wear out, from 
the ends in. 

Recently it has been found that telomerase, the enzyme that makes 
telomeric DNA, is expressed in immortal cells but not in normal cells. I 
imagine that telomerase is expressed at some stage in the development of 
a vertebrate, so that each new generation has its alotted lifetime of 
chromosome. If telomerase could be switched on at will, or better still 
swtiched on whenever telomeres get too short, then our chromosomes might 
keep better, and longer.

Dan Jeffares

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