As everyone probably already knows, many of our breeds and mixes have conditions that may have genetic origins. Some of the most common ones are hip and/or elbow dysplasia, hypothyroidism, progressive retinal atrophy, several types of heart disease, congenital deafness, tendency toward gastric dilatation/volvulus and many more. Below are some reference sites to help you learn more about these. While most don't prevent your dog from becoming well trained and well behaved, they may required that the training goals and process be modified to accommodate the dog's needs.