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Telomeric Theory - Those Damn Mice

Tom Matthews tmatth at netcom.ca
Mon Sep 7 15:39:02 EST 1998


Excelife wrote:

> Those cells that normally require telomerase, like the germ cells, in Dr.
> Greider's knock out mice, are affected by the absence of the gene coding for
> telomerase.  After around six generations the telomeres in the germ cells are
> too short to support additional replications and the mice are sterile.  But
> the cells not requiring telomerase had their telomeres replenished during
> embryonic development of each generation by the genes described above.
> 
> The answer to the first question, why the mice and their cells die with such
> long telomeres, was also amazingly simple.  It seems that some mice
> chromosomes have significantly shorter telomeres than the other chromosomes.
> Their length is such that they could cause a cell to enter senescence after
> approx. 10 population doublings, which is exactly what is observed in the
> studies of the mice.  Yeast studies have shown that the loss of a single
> telomere can result in cell-cycle arrest and chromosome loss.

I see a potential contradiction between these two paragraphs. While I
appreciate that the mechanism of germline DNA generation does not
operate with intact chomosomes, even so would it not be likely that
these short telomere ends on *some* chromosomes, which you are using to
explain the short mouse lifespan, would also differently affect the
germline chromosomes.

It appears to me that you are simply applying each argument in the best
possible way to "explain" your "desired" solution and at the same time
ignoring other equally reasonable explanations which don't fit your
"desired" paradigm.


--Tom 
Tom Matthews
 
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