The K Locus: Dominant Black, Brindle, and Non-Brindle

The K locus plays a critical role in determining whether a Dutch Shepherd expresses brindle or not. The locus has three primary alleles that impact coat color:

• KB (Dominant Black): This allele prevents any brindle or fawn expression and results in a solid black coat. While not typically seen in Dutch Shepherds due to historical breeding selections, it is theoretically possible to appear.

• kbr (Brindle): This allele allows brindling to appear over the base coat color determined by the A locus.

• ky (Non-Brindle): This allele allows for the full expression of the base coat color, meaning a dog with two copies of ky will not have brindle.

Brindle is only visible when a dog has at least one kbr allele without the more dominant KB allele being present. A dog with a base color determined by the A locus but carrying a copy of KB will be solid black, masking any brindle expression.

These pictures show an example of both brindle and non-brindle littermates (center) resulting from the cross of two brindle parents that both carry for ky.

The Challenge of Testing for Kbr

Although genetic tests can accurately identify KB and ky alleles, the kbr (brindle) allele presents a unique challenge. Many genetic testing companies do not offer direct kbr identification due to technical difficulties in distinguishing the allele. The complexity arises because kbr allele is a “complex segmental duplication” which means that the kbr allele is a doubling of the K locus on a chromosome, with one copy represented by the Ky allele and the second by the KB allele.  This makes it difficult to determine the difference between the combined kbr allele and the individual KB and ky alleles.  According to VetGenomics, advanced sequencing techniques and specialized markers are required to detect kbr accurately. Without such methods, most standard genetic tests cannot provide definitive confirmation. As a result, breeders often have to rely on pedigree analysis or test breeding to confirm whether a dog carries non-brindle.

Many K locus tests may infer the presence of kbr when brindle is observed in a dog's phenotype, but direct confirmation remains elusive.  For example, in the United States at this time, genetic testing laboratories typically report results for the K locus as either KB/KB, KB/ky, or ky/ky. Because kbr carries characteristics of both KB and ky, standard testing methods do not differentiate between kbr/kbr and kbr/ky, meaning brindle dogs often receive the same result as a non-brindle carrier of KB and ky. This limitation further complicates accurate genetic identification of brindle Dutch Shepherds.

Above, you can see a representation of the different alleles of the K locus.  You can get a picture of how the kbr allele is a duplication of the K locus on one chromosome, with one copy of the KB allele and one copy of the ky allele.

The A Locus: Determining Base Color

The A locus determines the underlying color that brindle overlays. In Dutch Shepherds, the relevant alleles include (in order of dominance):

• ay (Fawn): This allele produces a fawn base coat. When a dog carries brindle (kbr), the fawn color is overlaid with brindle striping.

• aw (Wild Type/Wolf Sable): This allele produces a black tipped hair pattern similar to what is seen in wild canids but is not common in Dutch Shepherds.

• at (Tan Point/Black and Tan): This allele produces a black-and-tan pattern similar to a Doberman or German Shepherd Dog, though it is rarely seen in Dutch Shepherds due to the prevalence of specific color selection.  In dogs that express kbr with an at base coat color, the brindle is only seen on the tan markings.

• a (Recessive Black): This allele results in a solid black coat if no other dominant alleles are present but is almost never, if ever, seen in Dutch Shepherds.

  Photo A displays a dog with an ay base coat.  Notice the clearly visible striping pattern. Photo B shows a dog with an aw base coat.  You can see the black tipped hairs along the back of the dog that muddies the appearance of the stripes. Photo C is representative of an at base coat.  Note that although the entire dog is brindle, the brindle pattern is only visible in the lighter markings of the dog.

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The D Locus: Dilution and Its Impact on Brindle

The D locus affects the dilution of coloration in a dog’s coat. The D locus has two primary alleles:

• D (Non-Dilute): This is the dominant form and does not impact coat color.

• d (Dilute): This allele, when inherited in two copies (d/d), dilutes black pigment to blue and red/fawn pigment to a lighter cream. In brindled Dutch Shepherds, this dilution can cause black brindling to appear grayish-blue instead of deep black.

Since dilution is inherited recessively, a dog must inherit two copies of d to express the diluted coat color. Carriers (D/d) will not show dilution but can pass it on to offspring.

Above is an example of the expression of d/d in a brindle Dutch shepherd.  As you can see, all areas with black coloration, including the nose, are lightened to a blue-gray color.

The E Locus: The Black Mask

The E locus is responsible for the presence of a black mask in Dutch Shepherds. The primary allele of interest is:

• EM (Black Mask): This allele causes a dark mask to appear on the muzzle and sometimes extends over the ears and face. It is commonly seen in brindle Dutch Shepherds and is the preferred color expression.

• E (Normal Expression): This allows for expression of coat color without a black mask.

A dog with at least one copy of EM will exhibit a black mask, which does not interfere with brindle expression but may cover facial striping.

In photo D, you can see an example of a Dutch Shepherd without a mask, while in photo E, you can see a dog expressing the EM allele with an obvious black mask.

The Impact of Brindle Striping Intensity

The appearance of a brindle Dutch Shepherd is influenced by the intensity of its black striping. A dog with heavy, thick black striping will appear darker overall, sometimes giving the illusion of a black dog with lighter-colored stripes, or even appearing solid black from a distance. This can be referred to as “reverse brindle” in some breeds, but in Dutch shepherds, this is just referred to as “dark brindle”.  Dark brindle is a more correct term for these dogs since the lighter color is always the base coat, and the black appears as stripes overlaying it. Conversely, a dog with thinner or more widely spaced striping will have a more pronounced fawn or sable background, making it appear lighter. The variation in striping can make brindle coats highly unique, with some dogs appearing almost entirely black while others display a more balanced pattern.  Too much black is a fault in the breed standard and is not desirable. 

Each of the brindle dogs in these photos have A locus results of ay/ay.  The intensity of the black striping is responsible for the difference in coloration. 

Labs Offering kbr Testing

While not all genetic testing companies can directly identify the kbr allele, some advanced laboratories have made strides in brindle identification:

• Labogen – Located in Germany, Labogen offers direct testing for kbr, providing breeders with a more definitive analysis of brindle inheritance.

• VetGenomics – Located in Russia, VetGenomics provides specialized testing for kbr using advanced sequencing techniques.

Importance of Genetic Testing for Dutch Shepherd Breeders

Since brindle is a hallmark of the Dutch Shepherd breed, responsible breeding practices require careful attention to the K, A, D and E loci. Understanding these genetic factors helps breeders maintain breed standards and avoid introducing non-traditional colors. While direct testing for kbr remains difficult, continued advancements in canine genetics may improve the accuracy of coat color testing in the future. 

By utilizing genetic testing alongside pedigree analysis, Dutch Shepherd breeders can preserve the unique brindle coat that defines the breed while ensuring genetic diversity and health remain a top priority.