Recessive Black (a)

A recessive black dog has a solid dark coat. This base pattern is caused by having two copies of a recessive loss-of-function variant at the A locus, which is why it is called recessive black.

What is Recessive Black?

The A locus holds the gene for ASIP. All patterned dogs need ASIP to produce phaeomelanin (yellow pigment). And the recessive black variant (a) represents a broken ASIP gene.

In other words, a dog with two broken ASIP genes (a/a) has very little or no yellow pigment.

A recessive black dog lost the ability to switch from eumelanin to phaeomelanin. Instead, it will have a solid dark pattern in any of the possible base colors (black, brown, blue, lilac).

Black is the wild-type color of eumelanin, the pattern name uses it as a placeholder for any colro of eumelanin. So a recessive black dog can also be solid brown, solid blue, or solid isabella/lilac!

Sometimes, the recessive black pattern still shows residual phaeomelanin markings. This causes some a/a dogs to have some smutty or faint tan markings on the paws or lower legs.

The a allele

Recessive black got its name to distinguish this recessive A locus pattern (a/a) from the dominant black pattern (KB/-) found at the K locus (which also causes a solid dark pattern).

Recessive black is one of the A locus patterns.

All recessive black dogs can express their A locus pattern (they can be ky/ky or kbr/-).

They can’t be recessive red (e/e, solid yellow) or dominant black (KB/-, solid dark) at the same time. So the E locus and K locus control, if a dog can express its recessive black pattern.

Much has changed in our understanding of the A locus in recent years. But not much has changed regarding our explanation of recessive black:

This solid dark phenotype is caused by a loss-of-function mutation in the ASIP gene. Without ASIP, the pigment cells will not produce phaeomelanin and instead produce only eumelanin.

DY	Ay	Dominant Yellow, Clear Sable
SY	Ays	Shaded Yellow, Shaded Sable
AG	aw	Agouti, Wolf Grey
BS	asa	Black Saddle
BB	at	Black Back, Tan Point
a	a	Recessive Black

Any combination with one of the more dominant alleles at the A locus (e.g. Ay/a) will give the pigment cells the ability to produce phaeomelanin and override the recessive pattern.

Only dogs with two loss-of-function copies (a/a) can express this pattern.

All the bi-colored patterns found at the A locus are caused by variation in two newly described regulatory regions of the ASIP gene (for more information on this, see the A locus.).

Different combinations of the ventral promoter (VP) and hair cycle promoter (HCP) represent the different A locus alleles and their different phenotypes^[1].

Phenotype	Allele	VP	HCP
Dominant Yellow	Ay	VP1	HCP1
Shaded Yellow	Ays	VP2	HCP1
Agouti	aw	VP2	HCP2
Black Saddle	asa	VP1	HCP4
Black Back	at	VP2	HCP3 HCP4 HCP5
Recessive Black	a	ASIP	ASIP

Recessive black stands out from the other patterns, since it doesn’t matter which promoters a dog has. The recessive ASIP gene is broken and will not induce phaeomelanin anyway.

The loss-of-function mutation originally happened in a VP2-HCP3 (at) variant. Many testing companies report both at and a, if they detect recessive black. This can be super confusing, since this mutant “at with a” variant now is “a” and no longer functions as “at“, so why report both?

Being a recessive black carrier can decrease the overall amount of ASIP available during hair growth and make a pattern darker than expected. For example, many dogs with Ay/a express darker sable, dogs with aw/a express darker agouti, asa/a can give creeping tan, and at/a often gives smaller tan points.

Many breeds that aim for a solid dark coat color have both recessive black (a) and dominant black (KB) in their gene pool, e.g. German Shepherd Dog, Schipperke, or Mudi.

Sometimes, the only way to determine a dog’s allelic status is testing or doing some pedigree analysis.

Two dogs with any of the yellow + black patterns (ky/ky or kbr/-) don’t have KB and can never produce a KB/- puppy. In this scenario, both parents are more likely recessive black carriers.

For example, two sable Shelties that produce a black puppy are both E/E ky/ky Ay/a. Or two tricolor Aussies that produce a black puppy have to be E/E ky/ky at/a.

Recessive Black Patterns

A recessive black dog usually has a solid coat color in all pigmented areas.

But sometimes, dogs with this coloration still express some smallish tan markings around the eyes or residual tan bleed-through on the lower legs or rear.

And some other traits can change how a recessive black dog looks, of course.

Recessive Black Colors

When talking about coat color genetics, the term “black” is often used as an umbrella term for all the different colors eumelanin can have.

A recessive black dog can be black, yes. But it might just as well also be liver, blue, or lilac. The actual color on a particular dog depends on its B locus and D locus.

Some examples for other colors than black may be found in solid blue or liver Mudis, brown & white (“red bi”) Australian Shepherds, or some color-bred German Shepherd Dogs.

Recessive Black & White

White markings can delete some or all of the dark pigment from the coat.

Bi-black Shelties or Aussies are common examples of recessive black & white.

Recessive Black & Ticking

In some dogs, any white spotting may develop ticking or roan. These spots show the color “underneath the white“. So on a solid black dog, all the ticking or roan will also be solid black.

This is a common pattern in many hunting dogs, e.g. roan in Wirehaired Pointing Griffons.

Recessive Black & Merle

Merle can cause a variety of phenotypes by deleting some of the pigment (mainly eumelanin) from a pattern. There are not many breeds that can produce both recessive black and merle at the same time. One example that comes to mind is “bi-blue” in Shelties.

Recessive Black & Graying

Graying causes eumelanin to fade from black to gray or from brown to beige colors. This trait somehow only affects furnished dogs, like some Affenpinschers, Poodles, or Pumis.

Recessive Black & Domino

The domino variants at the E locus (Northern domino or grizzle domino) reduce the amount of eumelanin in any given pattern.

Some recessive black dogs with domino may look very patterned instead of solid black. Their phaeomelanin markings can resemble a dark grayish smutty tan point or agouti pattern.

This rare combination can be found in some Northern breeds like the Finnish Lapphund.

Dog Breeds With Recessive Black

Some dog breeds have the recessive black without being able to actually express it. That is because a recessive red dog like a Samoyed or Golden Retriever with e/e a/a can’t express eumelanin.

And a dominant black dog with KB/- a/a will be solid dark anyway, because its KB allele overrides any of the A locus patterns under a solid dark coat.

All in all, recessive black is quite rare and can not be distinguished from dominant black just by looking at the dog, unless the dog shows obvious signs of either tan bleed through (a/a) or ghost tan (KB/-).

• Affenpinscher
• Alaskan Klee Kai
• Altdeutscher Hütehund
• American Bully
• Australian Shepherd
• Basenji
• Belgian Shepherd Dog
• Catahoula Leopard Dog
• Central Asian Shepherd Dog
• Cocker Spaniel
• English Springer Spaniel
• Eurasier
• Field Spaniel
• Finnish Lapphund
• German Shepherd Dog
• German Spitz
• Icelandic Sheepdog
• Irish Wolfhound
• Lagotto Romagnolo
• Lapponian Herder
• Mexican Hairless Dog
• Mudi
• Neapolitan Mastiff
• Papillon
• Poodle
• Pomeranian
• Puli
• Pumi
• Scottish Terrier
• Sheltie
• Small Münsterlander
• Swedish Vallhund
• Tibetan Mastiff
• Tibetan Terrier
• Wirehaired Pointing Griffon

Learn More

Links

[1] Bannasch, D.L., Kaelin, C.B., Letko, A. et al. Dog colour patterns explained by modular promoters of ancient canid origin. Nat Ecol Evol 5, 1415–1423 (2021). https://doi.org/10.1038/s41559-021-01524-x

Image Credits

© Anna Dudkova/unsplash.com
© Niels Hansen/pixabay.com
© Duygu/pexels.com
© Isabella Rosa/unsplash.com
© cynoclub/canva.com
© Kurt Pas/canva.com
© eriklam/canva.com
© eriklam/yayimages.com
© dpcrestock/yayimages.com