The color pattern merle (also known as dappling) is characterized by darker "blotches" on a lighter background of the same pigment (e.g., blue merle in Collies, red dapple in Dachshunds).1 This trait is sometimes associated with congenital defects such as deafness and ophthalmologic abnormalities, such as microphthalmia (a congenitally small eye). Heterochromia iridis (a difference in color of the iris in the two eyes, or two different colors within one iris) has also been associated with merle coloring, and is a disqualification for several breeds. An autosomal, incompletely dominant trait, merle coat coloring predisposes dogs to inherited deafness. When inherited in the homozygous state, the merle mutation causes dogs to be white and have an even greater incidence of deafness, blindness and sterility.2
The auditory and ophthalmologic abnormalities linked to merle are similar to those observed for the human auditory-pigmentation disorder Waardenburg syndrome. Characterized by varying degrees of hearing loss and changes in skin and hair pigmentation, another common trait is two differently colored eyes. Researchers have identified causative mutations in at least five genes for Waardenburg syndrome; however, the genetic bases for all cases have not been determined.
- See more at: http://www.akcchf.org/research/success-stories/gene-for-merle-color-pattern.html#sthash.fWIufQNh.dpuf
The auditory and ophthalmologic abnormalities linked to merle are similar to those observed for the human auditory-pigmentation disorder Waardenburg syndrome. Characterized by varying degrees of hearing loss and changes in skin and hair pigmentation, another common trait is two differently colored eyes. Researchers have identified causative mutations in at least five genes for Waardenburg syndrome; however, the genetic bases for all cases have not been determined.
- See more at: http://www.akcchf.org/research/success-stories/gene-for-merle-color-pattern.html#sthash.fWIufQNh.dpuf