Double-muscled dog

She's for real! This is Wendy, a double-muscled whippet who lives on a farm in Canada. The condition is due to naturally occurring mutations in the gene that produces myostatin, a protein that blocks growth of skeletal muscle. Myostatin deficiency occurs in many animals, including cows and sheep, and also occurs - rarely - in humans. Pharmaceutical companies are developing ways to mimic myostatin gene mutations to treat muscular dystrophy, cancer, and obesity and other metabolic disorders. Double-muscled Belgian Blue cattle have been bred since the 1950s for their abundant lean meat, but critics call for eliminating the strain, which is often unable to give birth naturally. The harnessing of the gene also has obvious implications for bodybuilders, but does shorten the lifespan.