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
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.