M-locus (atypicl merle, merle, cryptic merle) **

Tan-colouring is versatile in the propotion of dark and light marks. This gene regulates the... more
Disease
Merle is a coat pattern characterized by dark patches intermingled with diluted pigment. This trait is inherited in an autosomal, incompletely dominant fashion. Additionally, a shortened version of the causative M variant exists on the M-locus. This so called cryptic merle (Mc) has no influence on the coat colour itself. Merle coloured dogs therefore possess the genotypes N/M or M/Mc. Dogs homozygous for merle (M/M) are also known as double merles and are predominantly white. In all breeds, the double merle genotype can be sublethal and is associated with multiple auditory and ophthalmologic abnormalities. For these reasons, merle-to-merle breedings are strongly prohibited to avoid pain breeding. Although rare, a dog that does not exhibit the overt merle phenotype may possess the merle genotype and subsequently produce merle offspring. Such a dog is termed a phantom merle. Therefore, a genetic test is strongly recommended for stud-dogs in merle or merle related breeding lines.
Breed
All breeds
Heredity
autosomal dominant
Test duration
1-2 weeks after arrival of the sample in the lab
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