Double Merles, or Homozygous Whites are the result of breeding two merles (either blue or sable) together, and thus transmitting to the offspring two merle genes. These homozygous merles, often called "Double Merles", appear white with a few spots of diluted color. They are not genetically white, but a dilute created by the doubling of the merling gene. Many of these individuals are defective in sight or hearing or both. A few have been born without eyes, and many have very small or undeveloped eyes. 

NOTE:  These defects are color linked, and have NO effect on normal colored offspring produced by a double merle!!

Homozygous whites can be extremely valuable in a blue breeding program. When bred to a tri or bi-black, they will produce almost 100% blue offspring, often with an exceptionally clear blue color that is most attractive. Homozygous whites occur in approximately a twenty-five percent ratio in merle to merle breeding's. Defective double merle whites in a litter will have no effect on the normal colored littermates, nor will they carry any defects. Listed below are the names of two very prominent Double Merles that have been influential in the breeding of AOAC‘s.  

Merle to Merle breedings should only be done by responsible breeders who are willing to stand behind any puppy they produce that may be affected as a result of doing such a breeding!

 

 

Follow the links below to see examples of two influential Double Merles... 

 

Shadow Hill’s Double Trouble, ROM

Shamont Ghost Of A Chance, ROM

 

*All of the above information was taken from the book Sheltie Talk by Betty Jo McKinney and Barbara Rieseberg

 

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Elementary merle genetics for newcomers