clones & telomeres & telomerase-less mice

Damien Broderick (
Fri, 16 Jan 1998 15:18:46 +0000

Several people have remarked that Dolly is already evidence against any
simple understanding of the role of telomere length. Here's a salient bit
(quoted without permission) from Gina Kolata's new book CLONE: THE ROAD TO
DOLLY AND THE THE PATH AHEAD (William Morrow 1997; Allen Lane 1997):

`More than 90 per cent of all the cell divisions that ever occur in an
animal's... life occur in the womb... If Dolly's telomeres had only a few
divisions to go, she could not possibly have made it through foetal life...

`...another problem with the telomere hypothesis: Eggs are packed with
enzymes that lengthen telomeres. [I assume she just means telomerase, and
that this is already in the cytoplasm of the host ovum. DB] In fact, one
of the first things eggs do when they are fertilized is to adjust the
lengths of the telomeres on their chromosomes. So if a clone started out
with telomeres that were too short, it is all but certain that the egg
would lengthen them' (pp. 204-5).

Okay, breathe easy for Dolly. But here's the kicker, something I haven't
read anywhere else:

`[Lee M.] Silver [of MOUSE GENETICS (OUP 1995) fame] told me that mouse
researchers have even created mice that do not have [telomerase]. The mice
seemed healthy... are now up their fourth generation [sans telomerase]...
yet to find anything wrong...' (p. 205).


Damien Broderick