Continuing Dr. Bell's Relative Risk Analysis theory, statistically. The offspring of an affected dog has a 100 percent chance of being a carrier. Continuing Dr. Bell's Relative Risk Analysis theory, statistically • The clinically normal full sibling of an affected dog has a 67 percent chance of being a carrier. Jerold S. Bell, D.V.M., clinical assistant professor of genetics at Tufts University School of Veterinary Medicine, Bell says • The parent of an affected dog has a 100 percent chance of being a carrier. Jerold S. Bell, D.V.M., says: If a breeding female has X amount of risk of being a carrier, breeding it to a low-risk mate can cut the carrier risk up to 1/2 X in the offspring, he says. However, if you breed three offspring, then you have added three times 1/2 X into the population. With relative-risk assessment, you have to combine the analysis with replacing the higher-risk parent and limiting the number of reproducing offspring For a defective recessive gene to be passed on, there must be a carrier parent in each generation. However, unless the ancestral carriers have produced affected offspring or were the offspring of affected dogs, they cannot be identified. If four generations separate the carrier sire and an obligate carrier ancestor, then it is possible the shared ancestors between them could be carriers. 1 More factors for a Relative Risk Analysis Pedigree to be effective include: There must be an established open health registry database, such as the American Kennel Club Canine Health Foundation�s Canine Health Information Center (CHIC), that records the confirmed affected and carrier status of dogs. Important factors for a Relative Risk Analysis Pedigree to be effective include: * The mode of inheritance must be proven to be recessive * The pedigree information must be accurate and verifiable

Phenotype & Genotype. How a dog looks on the outside does not always predict what genes he is carrying and what he will produce. Example: A dog inheriting the gene pair Tt from his parents will have ticking, but because he "carries" the gene t for non-ticking, he is capable of producing dogs with non-ticking when bred to a bitch carrying the Tt or tt gene pair. The non-ticking would occur in any puppy that by chance happens to inherit his sire's t gene and a t gene from the dam.