Purebred dogs are more prone to getting canine genetic diseases than mixed breed ones because their gene pool is limited. Many genetic diseases in dogs are thought to be due to recessive genes. It's far more likely a purebred puppy will have both sire and dam containing the crucial recessive gene than a mixed breed. But it is still possible for a mongrel to have one of the hundreds of known canine genetic diseases. Of that huge number, here is a look at the most common.
Progressive Retinal Atrophy (PRA)
Also called progressive rod and cone degeneration, this is an irreversible disease of the eyes that always results in blindness. It always affects both eyes. There are a few types of PRA, but they differ usually in how rapidly the dog goes blind. Completely blind dogs actually cope better than people if given time and patience to adjust to their condition and if the owner goes through a bit of retraining in order to better cope with a blind dog.
However, there are very few people big-hearted enough to care for blind dogs. Many people will not bother and prefer to get rid of the blind dog and get a new one. This is one reason why PRA is such a problem. Many breed associations encourage their members to neuter any dogs with PRA, but they cannot force any member to do so.
In America, there is a national registration called the Canine Eye Registration Foundation. Anyone with sexually dogs, especially Irish Setters, is encouraged to get their dog's eyes checked with a CERF exam. A CERF certificate is highly prized.
"Dog Owner's Home Veterinary Handbook" (Debra M. Eldredge, DVM, et al: 2007) states that hip dysplasia is a common menace in large breed dogs, but has been seen in mixed breeds, medium sized breeds and small dogs. Also, more than one gene is needed to make a dog predisposed to hip dysplasia, so it very difficult to eliminate from the gene pool.
In hip dysplasia, the sockets of the leg joints become malformed, causing lameness and considerable pain. Fortunately, this is a treatable condition, although severe cases need surgery. It's important that any puppy or young dog with hip dysplasia never be allowed to get overweight, as this can injure the joints.
"Dog Owner's Home Veterinary Handbook" states that this is the most common genetic blood disease in dogs. This is a potentially deadly bleeding disorder where the blood does not clot. A small cut could lead to significant blood loss and doing minor surgery is difficult, at best. This genetic disease is found in many breeds such as the Akita, Manchester Terrier, Standard Poodle, Golden Retriever, Pembroke Welsh Corgi. Shetland Sheepdog, Dobermans, Miniature Schnauzers and Chesapeake Bay Retrievers.