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. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=26222