Breeding Guidelines

MDR1 Breeding Guidelines

This chart provides guidelines for consideration when owners are contemplating breeding dogs that may be affected by the MDR1 mutation.  While it is ideal to use only "Normal/Normal" breeding pairs, one must always consider other genetic factors in addition to the MDR1 gene. Because the MDR1 gene is present in such a large percentage of Collies and Australian Shepherds, it may be necessary to breed "Normal/Mutant" dogs in order to maintain a large enough pool of good breeding stock. By using thoughtful breeding strategies including these guidelines, future generations of dogs will have a substantial decrease in the frequency of the mutant MDR1 gene.

MDR1 Breeding Pair Combinations and Outcomes

Normal/Normal MaleNormal/Mutant* MaleMutant/Mutant Male
Normal/Normal Female100% Normal/Normal puppiesNormal/Normal and/or Normal/Mutant puppies100% Normal/Mutant puppies
Normal/Mutant* FemaleNormal/Normal and/or Normal Mutant puppiesAny combination of puppiesNormal/Mutant and/or Mutant/Mutant puppies
Mutant/Mutant Female100% Normal/Mutant puppiesNormal/Mutant and/or Mutant/Mutant puppies100% Mutant/Mutant puppies

*Normal/mutant is the same as mutant/normal and "heterozygote"