Percy brought up the point that you start from a mixed genetic background and end up with your breeds. This is exactly what happens and the mouse as a genetics model developed just this way....like dog breeds, there were mouse breeds. These were donated to the Jackson lab which then went on to make inbred lines of mice selecting for various traits. The entire project is to take as much variation away to look at the genetic basis of specific traits. The difficulty is that variation due to mutation is constantly popping up whether you want it to or not...in any case, dog breeds are far more complicated as to their origin and it they probably have a polyphyletic origin i.e. no one stock...
a references on dog evolution....
Science. 2002 Nov 22;298(5598):1613-6. Related Articles, Links
Comment in:
Heredity. 2003 Mar;90(3):201-2.
Science. 2002 Nov 22;298(5598):1540-2.
Ancient DNA evidence for Old World origin of New World dogs.
Leonard JA, Wayne RK, Wheeler J, Valadez R, Guillen S, Vila C.
Department of Organismic Biology, Ecology and Evolution, University of California, Los Angeles, CA 90095-1606, USA. Leonard.Jennifer@NMNH.SI.edu
Mitochondrial DNA sequences isolated from ancient dog remains from Latin America and Alaska showed that native American dogs originated from multiple Old World lineages of dogs that accompanied late Pleistocene humans across the Bering Strait. One clade of dog sequences was unique to the New World, which is consistent with a period of geographic isolation. This unique clade was absent from a large sample of modern dogs, which implies that European colonists systematically discouraged the breeding of native American dogs.
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