Jerold S. Bell, D.V.M., clinical assistant professor of genetics at Tufts University School of Veterinary Medicine, says that when there is no genetic test for carriers of an undesired genetic trait, the most objective tool for selection against recessive disorders is a relative-risk pedigree analysis It is more difficult to predict affected and carrier dogs for some genetic disorders than others. Polygenic traits, meaning two or more pairs of genes involved in heritability, can be extremely challenging for scientists to develop a genetic test. Hip Dysplasia is an example of a polygenic disease for which no genetic test has been developed. It is easier to predict affected and carrier dogs for disorders having an autosomal recessive mode of inheritance. In these cases, both parents of an affected dog are carriers, even though they may appear normal. As the number of carriers increase, so will affected dogs. Fortunately, it is possible to evaluate pedigrees for recessive trait risk and use this information to make informed breeding decisions. Relative-risk analysis does not identify carriers, just risk. Through pedigree analysis, you can lower your chance of producing carriers with each generation, but you must limit the number of breedable offspring, so as to not increase the carrier risk of the population.

From www.PurinaProClub.com: Using Relative-Risk Pedigree Analysis in Breeding Responsible breeders are selective about choosing the best dogs to breed. Beyond considering physical characteristics, temperament and colors, breeders try to avoid passing on genetic disorders. Unfortunately, breeders don’t always have the tools and information necessary to make educated decisions. It is more difficult to predict affected and carrier dogs for some genetic disorders than others. Polygenic traits, meaning two or more pairs of genes involved in heritability, can be extremely challenging for scientists to develop a genetic test. Hip Dysplasia is an example of a polygenic disease for which no genetic test has been developed. It is easier to predict affected and carrier dogs for disorders having an autosomal recessive mode of inheritance. In these cases, both parents of an affected dog are carriers, even though they may appear normal. As the number of carriers increase, so will affected dogs. Fortunately, it is possible to evaluate pedigrees for recessive trait risk and use this information to make informed breeding decisions.