K-locus brindle

LABOKLIN Service ID: 8893

The K locus plays an important role in the inheritance of coat colour, as variants at this gene locus determine whether the pigments are distributed uniformly or expressed separately in the individual hairs or on the dog's body. There are basically two different gene variants (KB and ky) which, when combined, lead to the three known alleles KB, kbr and ky and the associated effects on coat colour (uniform pigmentation, brindle, coat pattern).

If at least one dominant allele KB is present (genotype KB/*), this allele will be expressed. KB is responsible for a solid-coloured coat in the pigmented areas, as the pigments are expressed together or individually, but uniformly overall.

In contrast, the recessive ky allele allows the pigments eumelanin and pheomelanin to be distributed in relation to each other. The effects of the A locus on pigment distribution are only fully visible with the homozygous ky/ky genotype.

The allele kbr, which is responsible for the brindle, is a heterogeneous duplication of the variants KB and ky on one chromosome. The effect of this duplication can be seen in the brindle, i.e. dark (eumelanin) stripes on a light (pheomelanin) base colour. Brindle is only visible in those areas where a light colour is otherwise present (e.g. with black&tan colouring in the light markings). The kbr allele is recessive to KB, but dominant to ky. The expression of the colouring is very variable and can vary from a few isolated stripes to almost completely dark dogs. It is not yet possible to make a statement about the expression of brindle via genetics.

Note: kbr can also be defined as KB+ky, which is why the KB/ky genotype is always determined in the classic detection of the KB and ky variants for dogs with at least one kbr allele. Therefore, only an additional analysis procedure for dogs with the KB/ky genotype in the classic K locus test enables the actual division into the possible genotypes KB/ky, KB/kbr, kbr/kbr and kbr/ky and thus also a correct statement on the possible inheritance of this trait.

Depending on the breed or colour of the dog, the simple K locus test may be sufficient, or a combination of analysis methods may be necessary.

 

K locus KB (uniform pigmentation) > kbr (brindle) > ky (coat pattern)
Genotype	Inheritance	Phenotype
KB/KB	does not inherit brindle or coat pattern	uniform pigmentation in pigmented areas
KB/kbr	can inherit brindle
KB/ky	can inherit coat pattern
kbr/kbr	does not inherit coat pattern	eumelanin stripes on pheomelanin base
kbr/ky	can inherit coat pattern
ky/ky	always inherits coat pattern	pigments can be distributed in relation to each other ⇒ A locus

Duration

1 - 2 weeks after arrival of the sample in the lab