Simply put, if one parent is clear and one is a carrier, it should result in pups who are either clear or carrier, so none should go on to develop the disease. IF it were that simple …
As you are probably aware, DM is believed to be an autosomal-recessive condition ie dogs have to inherit two copies of the DM gene mutation (one from each parent) to increase the risk of developing this condition. However the disease isn’t completely understood (there are thought to be environmental and other genetic predispositions that may contribute) and there is actually a question mark over the test itself. Other factors that influence whether or not a dog is affected by this condition means that having two copies of the recessive mutant gene does not necessarily always result in clinical disease and similarly an absence of the gene is not a guarantee that the condition will not occur.
For a small donation to GSD Rescue the GSD Breed Health Coordinator will check both parents pedigrees and look for any other potential health issues to take into consideration.
one of the great things about this forum is knowledgeable people sharing their experiences. i have learnt so much about other breeds. i mostly have mixed breed dogs ,lurchers and terriers and the only purebred kc registered one was my deerhound, my favourite breed..
Also worth remember that each fertilisation is an independent action, this means that the percentages mentioned is for each puppy, and not for the litter.
For instance mating two carriers doesn’t mean that 25% of the litter will end up being affected (or “at risk” as it more correctly is). It means that for each puppy, there is 25% chance of being born with two affected genes (and therefore of course being “at risk”).