Must an AGING PROCESS be universal? was Defining...

[Patrick O'Neil]

On Tue, 28 Mar 1995, Oliver Bogler wrote:

> When considering ageing as a process of cells, rather than organisms, then
> it is clear that some cells, such as bacteria, or parts of organisms,
> don't age. The germline is an unbroken lineage going back to the origin of
> life, 

Even bacteria, in the strictest sense, cannot be considered immortal.  
They have to actively and constantly replicate or die.  The daughter 
cells, due to the inherent error rate of DNA polymerases, ensures that 
none are the exact replica of the progenitor.  If you were to do the 
equivalent, you would be a big lump of ever-dividing cancer.  

Quiescent cells are not immune to damage, which is inevitable, so they 
do, in fact age.  In the very least, if you wish to dispense with the 
idea of aging in these particular cases, then just existing for a period 
of time demands that damage will occur for which the cell cannot 
recover.  Eventually, then, such cells will die and it will be FAR sooner 
than 200 years.

The germline is not itself an unbroken replicative chain.  Since 
replication in the process of meiosis is occuring at a high rate in 
germline cells, errors are also occuring.  No sperm or egg is going to 
carry the exact same DNA makeup as the parent.  Hell, it is unlikely that 
you could find two cells in your body within which the base sequences 
are absolutely identical.  With the size of our genomes coupled to the 
normal mutation rate of replication, you are certain to have at least one 
erroneous base incorporation in each cycle.  
 
You can, perhaps, decrease the natural error rate to below 10^-10 or 
10^-11 per basepair per replication cycle, but you cannot prevent error 
entirely, so time-related deleterious mutations are inevitable.  Call 
THAT aging if you wish.

Patrick