As Breeders Test DNA, Dogs Become Guinea Pigs:
When mutant, muscle-bound puppies started showing up in litters of champion racing whippets, the breeders of the normally sleek dogs invited scientists to take DNA samples at race meets here and across the country. They hoped to find a genetic cause for the condition and a way to purge it from the breed.It worked. “Bully whippets,” as the heavyset dogs are known, turn out to have a genetic mutation that enhances muscle development. And breeders may not want to eliminate the “bully” gene after all. The scientists found that the same mutation that pumps up some whippets makes others among the fastest dogs on the track.
So it works a bit like the famous sickle-cell gene: one copy confers the sickle-cell trait and protection from malaria, while a second copy leads to sickle-cell anemia and terrible health problems:
It’s not just whippets who have muscle-building myostatin-related mutations, but Belgian Blue cattle, Flex Wheeler, a German toddler, and a Michigan toddler.