X-Message-Number: 26222
From: "Basie" <>
Subject: laboratory rodents
Date: Sun, 22 May 2005 22:45:46 -0400

This has been done in laboratory rodents, producing inbred strains of mice 
and rats so similar genetically that they easily tolerate skin or organ 
grafts from other animals from the same inbred strain. However, the process 
of inbreeding used to create these strains generally results in loss of 
fertility (first seen in these mammals as a reduction in litter size) which 
actually kills off the majority of the strains between 8 and 12 generations 
of this extent of inbreeding. A handful of the initial strains survive this 
bottleneck, and these are the inbred laboratory strains. However, very 
little selection other than for viability and fertility is possible during 
this process. You wind up with animals homozygous for a more or less random 
selection of whatever genes happened to be in the strains that survived, all 
of which derive from the parents of the initial pair.

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