In dogs, a genetic variant that produces dark coats in standard poodles also predisposes them for squamous cell carcinoma — a type of skin cancer, Ostrander explained. "Nobody's trying to breed poodles who get squamous cell Canine's Delight carcinoma," she told Live Science. "But the variants are really close to each other in genome, so if you select for one, the other will truck along with it." Both the AKC and CFA are tracking scientists' findings about the genetics of cat and dog breeds, "and are trying their best to not allow bad things to happen with the good things they want as well," Lyons said. "But sometimes, the trait that you're selecting for in the first place may not be a good idea," she added. Certain exaggerated physical traits can introduce health problems, particularly in dog breeds, Ostrander said. The wrinkly faced shar-pei's signature skin folds can harbor bacteria that lead to infections, while breeds of dogs and cats with dramatically shortened skulls can suffer from breathing issues, Ostrander explained. However, a growing number of breeders in recent decades have been working to reign in some of the most extreme variations of these traits and are investigating breeding strategies that incorporate growing reservoirs of genetic data to produce healthier animals, according to Ostrander. "It was not an easy sell to breeders 20 years ago — to say, 'You have to change the breed standard,'" Ostrander told Live Science. "But they get it now. The trick here is not to throw out of breeding programs every [animal that is a] carrier of a recessive disease , but don't breed carriers to carriers.