When the inheritance is simple recessive the most carriers will be produced in pairings, where one of the parents is a carrier free from symptoms of the disease and the other parent is totally free from the defected gene. None of these puppies will show symptoms of the disease, but every second puppy ( 50 % ) will be a carrier of the disease. View the inheritance here.
You cannot totally eliminate a recessive defect gene but you can help to make the frequency low by trying to avoid breeding on carriers of the disease. The problem is to try to identify carriers free from symptoms. You can proceed as follows:
* All known carriers free from symptoms will be marked in the pedigree. These are the dogs that have produced affected puppies or they have any affected parent themselves.
* In the pedigree of the dog you want to use
1) there ought not be any known carrier in the first parent generation (neither father nor mother ought to be a carrier)
2) at most one carrier in the second parent generation (grandfather -…- grandmother)
3) at most two carriers in the third parent generation (grandgrandfather -…- grandgrandmother)
4) step 2 and 3 may not be combined.
If you follow these simple instructions there will be less than 50 % risk of that the dog you want to use is a symptomless carrier of a recessive defect. This method can be used for one or more simple recessive defects at the same time.
Finally, it is stated that a dog breeder who avoids to make use of dogs with a risk of 50 percent or more to carry the defect trait and who also can reduce the risk for the defect trait in each dog generation has a reasonable chance to be successful in the selection against the defect.
Do not use LHASA APSOS for breeding if they not are eye tested and diagnosed
unaffected for PRA within at least a year before mating (both male and female).