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: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1360527/?tool=pubmed
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.