Genetic defects

I thougt it was that you breed dogs. Cull anything that is not 100% then breed those and keep going until the defects are bred out of the line. To me the worst thing you can do is breed a dog with a known defect. Now that is different than something undesirable. If a dog has a behavior issue you can breed to a dog without it for a stronger hunter but you do not breed the pups with the behavior issue. But as far as genetics you have to work hard to remove those problems. That is like putting boards with termites in the house you are building thinking you can get rid of the termites later. Just use the boards without termites to begine with and save yourself all the headaches.