Inbred dogs are offspring of inbreeding. Inbreeding is the act of mating dogs that are closely related. For example, the mating of parents and offspring or the mating of siblings. Through inbreeding, many bloodlines could be perfected and individual dog breeds can come into
Inbred dogs have very similar genes with their parents and scientists have found out that inbred dogs with Higher COIs (coefficient of Inbreeding) are more prone to sickness. Genes carry the code or instructions for every aspect of a dog, how it would look and function, its personality as well. Sometimes things go wrong and genes are faulty or begin to work in the wrong ways and this is where the problem starts.
Fortunately, inbred puppies get two copies of each gene from each parent and so the working one overrides the broken one. Usually, there are not many copies of a faulty gene roaming about in a generation so the overriding works, but more closely related individuals are more likely to share the same faulty gene.
Some of the challenges of inbred dogs are reduced life span. Furthermore, inherited diseases spring up as many faulty genes meet. Also, fertility and litter sizes are affected.