Clemson Canine Genetics

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Merle Testing

Merle Coat Patterning


Merle is a pattern that randomly dilutes the base coat color to cause a marbled appearance.

"Cordell" (Owned by Kathy Moll) 
A merle collie.






Merle is caused by an insertion in a pigmentation gene known as SILV. Download the article describing this research here:




A test for merle is available through IDEXX. The test must be ordered through a licensed veterinarian who has an account with IDEXX Laboratories. The test requires either 2mL of blood in an edta (purple-top) tube or 1-2 cheek swabs. I recommend submitting blood. The test code is 3341 (MER). Results usually take 5-7 working days. If your veterinarian has questions about the test, he/she should call IDEXX at 1-888-433-9987. They will only speak to a veterinarian with an IDEXX account.


Merle, denoted by M, is dominant. Non-merle dogs are depicted in black, but may have any coat color or pattern other than merle. The above Punnett squares show the expected outcomes from a merle to non-merle mating (left) and a merle to a merle mating. The latter may result in white progeny with defects of the eye and/or ear.


"Morgan" (Owned by Dr. Jacquelyn Wahl) 
A double merle Australian shepherd.
"Morgan" is bilaterally deaf.