The Merle gene creates patches of colour in the coat and blue or odd-coloured eyes. Merle dogs may have hearing and eye problems. Dogs homozygous for Merle, also known as double Merle, are predominantly white and prone to several health problems. Merle can be tested in any breed, but is most often found in the breeds listed below.

Transmission

Incomplete dominance

Breed

American Bully, American cocker spaniel, American Pit Bull Terrier, American Staffordshire Terrier (Amstaff), Bulldog, Cardigan Welsh Corgi, Catahoula Leopard Dog, Chihuahua, Dachshund, French Bulldog, Great dane, Great dane, Pomeranian, Pyrenean Shepherd, Rough Collie, Staffordshire Bull Terrier, Australian Shepherd, Border Collie, Old English Sheepdog, Shetland Sheepdog, Beauceron