Quote Originally Posted by sorraia View Post
I have to disagree with you, pretty much completely.

Lab rats and mice are not a subspecies, they are the same species as pet/feeder rats and mice. They are no different morphologically, their chromosomes are the same, and the only differences in genetics is what genes and alleles were selected for or against in the lab rats and mice. Lab rats and mice were inbred for many generations, and during that time different lines and strains were developed for different purposes. Some were developed for control purposes, some selected for cancers, some for diabetes, some for obesity, etc. This was all achieved through carefully recorded, well monitored, and highly selective inbreeding. Through inbreeding those genes coding for that desired trait were selected for, while those genes coding for undesired traits were selected against.
umm, no. time for some sources.

http://en.wikipedia.org/wiki/Knockout_mouse

"A knockout mouse is a genetically engineered mouse in which researchers have inactivated, or "knocked out," an existing gene by replacing it or disrupting it with an artificial piece of DNA. The loss of gene activity often causes changes in a mouse's phenotype, which includes appearance, behavior and other observable physical and biochemical characteristics.
Knockout mice are important animal models for studying the role of genes which have been sequenced but whose functions have not been determined. By causing a specific gene to be inactive in the mouse, and observing any differences from normal behaviour or physiology, researchers can infer its probable function."

so no, the varieties of lab rats / mice you mention are not line-bred. they are genetically engineered by selectively destroying one of their genes. no carefully selected inbreeding. you take the digital mouse genome, scan for the gene, synthesize a new strand of DNA that contains a destroyed version of the gene, splice that into stem cells of the mouse, put these into a zygote, fertilize it and implant into a female mouse, and you get a "het for knockout" baby. breed back to get homozygous knockout mouse.


check out this one:
http://en.wikipedia.org/wiki/BALB/c

it went through 26 generations of sibling to sibling inbreeding from 1920 to 1935. one substrain reached its 235th generation of inbreeding in 2005. inbred lab mouse strains are typically inbred for over 100 generations.

there is only one trait that would require the insane amount of 100+ consecutive generations of sibling to sibling inbreeding, and that trait is a simplified genome from which randomness and heterozygousness are almost totally eliminated.