Merle (coat colour in dogs)

Merle is a color combination in dogs’ coats. It is a solid base color (usually red/brown or black) with lighter blue/gray or reddish patches, which gives a mottled or uneven speckled effect. Although most breeds that can have merle coats also typically have white markings (such as around the neck, under the belly, and so on), and often tan points (typically between the white and the darker parts of the coat), these are separate colors from the merle; some dogs do appear completely merled with no white or tan markings.

Merle can also alter other colors and patterns besides the usual red or black. These combinations such as Brindle Merle or Liver Merle are not typically accepted in breed standards.

In addition to altering base coat color, merle also modifies eye color and coloring on the nose and paw pads. The merle gene modifies the dark pigment in the eyes, occasionally changing dark eyes to blue, or part of the eye to be colored blue. Since merle causes random modifications, however, both dark-eyed, blue-eyed, and odd-colored eyes are possible. Color on paw pads and nose may be mottled pink and black.

Merle is a distinguishing marking of several breeds, particularly the Australian Shepherd, and appears in others, including the Koolie, German Coolies in Australia, the Shetland Sheepdog, various Collies, the Welsh Corgi (Cardigan), the Pyrenean Shepherd, the Bergamasco Sheepdog, the Catahoula Leopard Dog,and the Old English Sheepdog. In Dachshunds the merle marking is known as "dapple" [citeweb |url=http://www.dachshund.org/article_double_dapple.html |title=The Double Dapple |publisher=The Dachshund Magazine Online |accessmonthday=June 25 |accessyear=2007] . It is also present in the Pomeranian. In the Pit Bull, Chihuahua, and Cocker Spaniel breeds it is not, however, a recognized color. The merle gene also plays a part in producing harlequin Great Danes.

Merle is actually a heterozygote of an incomplete dominance gene. If two such dogs are mated, on the average one quarter of the puppies will be double merles ("double dilute") and a high percentage of these double merle puppies could have eye defects and/or be deaf. Knowledgeable breeders who want to produce merle puppies mate a merle with a non-merle dog; roughly half the puppies will be merles without the risk of vision or hearing defects.cite book |last=Coile |first=D. Caroline |title=Australian Shepherds |origyear=1999 |publisher=Barron's |isbn=0-7641-0558-2 |pages=20-21 |chapter=Obtaining an Australian Shepherd]

In January 2006, scientists at Texas A&M University announced the discovery of a mobile genetic unit called a retrotransposon, responsible for the merle mutation in dogs. [cite web |url=http://www.lsu.edu/deafness/ClarkPNASMerle.pdf |title=Retrotransposon insertion in SILV is responsiblefor merle patterning of the domestic dog |accessdate=2007-05-15 |last=Clark |first=Leigh Anne |authorlink= |coauthors=Jacquelyn M. Wahl, Christine A. Rees, and Keith E. Murphy |date=2005-11-26 |format=PDF |work=PNAS Early Edition |publisher=Louisiana State University ]

A phantom merle is one with such small patches of merle--or none at all--that it appears to be a non-merle. In America, a dog with the phantom merle coloring is described as being "cryptic for merle."

References

External links

* [http://bowlingsite.mcf.com/Genetics/Merle.html Genetics of merle dogs]
*: Basic, simple-language explanation of Australian Shepherd merle colorings
* [http://www.australian-shepherd-lovers.com/lethal-white.html Homozygous "Lethal White" Merles]