College of Veterinary Medicine

Veterinary Clinical Pharmacology Lab 

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 Male Normal/Mutant* Male Mutant/Mutant Male
Normal/Normal Female 100% Normal/Normal puppies Normal/Normal and/or Normal/Mutant puppies 100% Normal/Mutant puppies
Normal/Mutant* Female Normal/Normal and/or Normal/Mutant puppies Any combination of puppies Normal/Mutant and/or Mutant/Mutant puppies
Mutant/Mutant Female 100% Normal/Mutant puppies Normal/Mutant and/or Mutant/Mutant puppies 100% Mutant/Mutant puppies


*Normal/mutant is the same as mutant/normal and "heterozygote"
Last Edited: Jul 17, 2009 3:15 PM   

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