Version updated to reflect new discoveries regarding the Agouti series from 2022.

Yes, because sable or black and tan puppies, which have occasionally been born in recent years to two solid black parents, continue to surprise breed enthusiasts and experts. Aafter all, a knowledgeable shepherd dog fancier knows that this is supposed to be impossible! Whether they have a deep understanding of genetics or simply follow the charts explaining “what can come from what”, or rather, what “should” come from what, they know that from two completely black geman shepherds may born only completely black puppies. So, what is going on?

Well, there are two possibilities: either a random genetic mutation occurred, which isn’t strictly impossible, as such things happen all the time, though it is highly unlikely that “that specific” mutation would occur in “that specific” breed or, more likely, there was an introduction of “outside” DNA. We don’t know exactly what it was, we can only speculate. One hypothesis points to the Belgian Shepherd, given that the two breeds are closely related, share common origins, and have often been crossbred (even if the offspring were generally classified as mixed-breed). Others mention Russian breeds, since the dogs in question often originate from that region, while some claim that the dominant black trait has always existed in certain bloodlines. Of course, the Belgian Shepherd isn’t the only breed carrying the gene responsible for the phenomenon we are discussing, it could just as easily be a mixed-breed dog, provided it possesses “that gene.” In any case, even if it did stem from an outside introduction, something that remains unproven, any such influence would become negligible after just a few generations. The dogs revert perfectly to the breed standard, and DNA tests confirm them as 100% German Shepherd, so there is no issue.

So, before diving into the genetics itself, I’d like to take a brief detour to explore these “clandestine introductions”. People often hint at them, but can such a thing really happen? Well, it certainly happens, it has happened, and it will happen again. Parentage checks aren’t always performed, selected parents with DNA Stocked and certified pedigrees aren’t always used, and the offspring aren’t always registered as “selected” dogs, so yes, it happens, and in happens across all breeds. Sometimes it’s intentional, sometimes accidental, sometimes it’s discovered, sometimes not, sometimes even the dam’s owner doesn’t notice. However, if there are any doubts, there is always the parent-offspring DNA test to verify that everything is as it seems to be. It is precisely through litter checks, sometimes mandated by the Kennel Club, sometimes requested voluntarily by owners, that various cases of dog excanges come to light.
In fact, staff at a genetics institute told me that the most common scenario is a litter sired by two or more fathers. You see, not all available ova are necessarily fertilized at the same time, if the female mates with different dogs at different intervals, some unfertilized ova might be fertilized by a second (or even third) partner. An owner might return from the planned mating convinced the female is already pregnant and leave her with their own male(s),  if she mates again, she can end up with offspring from different fathers. Sometimes this stems from naivety, but other times it is done on purpose, an attempt to secure more puppies for sale in case she hadn’t conceived or only a few ova were fertilized.

That said, it follows that if any “othergenetic material” was introduced, it wasn’t necessarily done intentionally, and who knows how long ago it happened. Far be it from me to cast aspersions on anyone or anyone’s dogs, who knows me understand my stance, dogs should be healthy, in type, and have a good temperament. If those criteria are met, I have no issue with it, even if other genetic material found its way in over time. After all, as I’ve said, it happens constantly and always will. In any case, regardless of how these colors we’re about to discuss are achieved, they remain colors of breed’s standard, so everyone can rest easy. This article is not an exposé or an attempt to defame anyone, it is simply a genetic explanation of what occurs, intended to satisfy the curious and dispel any doubts. After all, whenever this happens, a debate inevitably ensues,or at least it did in the early days. By now, people have likely gotten used to it…

Let us now turn to the genetic series relevant to us specifically, those governing coat color in dogs.

First, let’s recall that the color BLACK is produced by EUMELANIN, while the color RED (fawn) is produced by PHEOMELANIN, these are the only two types of pigment that color a dog’s coat and body. The interplay of these colors, varying in intensity and distribution—combined with white markings (which aren’t actually a color, but rather the total absence of pigment), creates the infinite universe of possible dog coat colors, all orchestrated by just a few DNA loci.

THE AGOUTI SERIES

The most important genetic series, the one that determines what color our German Shepherd will be, is the famous AGOUTI series. It contains the alleles that dictate the distribution of black hairs, fawn hairs, or hairs with alternating bands of fawn and black across the dog’s body. There are 6 alleles in this series, although only 4 are found in the German Shepherd.

-A^y (from “yellow“) It is the primary, most dominant gene, the fawn (or fawn with black overlay) gene. theorically, this is the only one the Belgian Shepherd should possess (even when we see them looking black, you will understand why later), whereas it is absent in the German Shepherd. the example shown in the photo is a Belgian Malinois.

–A^ys (from “shaded yellow“) is the second in the order of dominance, this is the sable (or “shaded fawn“) coat, the only one, along with the Ay fawn, that the Belgian Shepherd theoretically possesses (even when it appears black,you will understand why later), but which is absent in the German Shepherd. Indeed, the example shown in the photo is a Belgian Malinois

–A^w (w from “wild“), also known as Agouti, grey, sometimes. It is called “wild” because it is the wild-type coloration, indeed, it is the color found in their wolf cousins, but it also appears in many other wild animals because it offers better camouflage. This color is frequently found in working lines, although, as we shall see, there are also Agouti dogs in show lines.

–A^s (s from saddled) The Classic  Show Line Black and Tan, with saddle retiredback from Shoulders.

–A^t   (t from Tan Point) It is the classic black-and-tan, beyond that, working lines generally feature the classic bicolors with “socks,” “near-total” blacks with minimal tan, or tan markings like a Doberman’s or even less. Even when they have more tan, however, they certainly lack the “saddle” markings seen on the show dogs in the example photo. Given the partial relevance of this point to the mystery the article aims to unravel, we will return to it in detail shortly

–a The most recessive of all, our famous “true” black, the only black a German Shepherd should have. Being the most recessive in the series, producing black dogs requires the subject to possess two ‘a‘ alleles at the agouti locus (referred to as being homozygous for ‘a‘), in other words, the ‘a‘ gene must have been inherited from both the mother and the father.

–A^w (w from “wild“), also known as Agouti, grey, sometimes. It is called “wild” because it is the wild-type coloration, indeed, it is the color found in their wolf cousins, but it also appears in many other wild animals because it offers better camouflage. This color is frequently found in working lines, although, as we shall see, there are also Agouti dogs in show lines.

This explains why so many mixed-breed dogs are either black (K-series) or fawn (agouti series, but a more dominant variant). These are the most dominant alleles within the genetic series that have the greatest impact on a dog’s coat color.

A^s : (from “saddled“) Black-and-tan with a saddle pattern,  is forth from the bottom in terms of dominance within the agouti series.

A^t :(from “tan point“) Dark black-and-tan, is fifth from the bottom in terms of dominance within the agouti series.

a: Recessive black is the least dominant of all.

A black German Shepherd will typically have the a-a genotype (homozygous for a), or at least that is usually the case; however, there are recent exceptions. Some black German Shepherds are actually “dominant black”, similar to the Groenendael, meaning that while their phenotype looks identical, they are genetically completely different, thereby overturning the beliefs we held prior to their appearance.

Recessive black (from the agouti series), when mated with another dog of the same type, can only produce black offspring;

dominant black (from the K-series), on the other hand, can produce all three colors found in the breed. I refer you to the article that explores this topic in greater depth.

This is also why we have briefly mentioned the K-series, which is responsible for dominant solid black.

Anyone who has bred or seen a black-and-tan German Shepherd puppy knows that, at a young age, they are almost entirely black with tan markings in specific locations. In some individuals, particularly those from show lines, these tan markings expand as the dog grows. By adulthood, only a saddle pattern remains, ranging in size from a broad patch to a mere stripe along the back. We will revisit and explain this point in more detail shortly.

The I (intensity) gene
The fawn coloration remains fundamentally the same, although different names have been given to its various shades, the color intensity within the fawn areas is actually regulated by another gene named “I” for intensity.  But is not the only one. This gene determines the amount of red pigment present in the fawn areas, resulting in individuals ranging from yellowish or nearly white tan points to those with such rich pigmentation that they display a deep, intense stag-red hue. Genetically, however, they remain identical, always either A^t A^s or A^w, because even in the agouti pattern, the intensity of the fawn color in the coat varies significantly from one dog to another, ranging from almost white to stag-red.

Indeed, the I gene acts on the fawn coloration, affecting all fawn areas across the body, regardless of the specific allele present in the agouti series.

It was once thought that dominant black also belonged to the agouti series, however, it has since been established that dominant black is caused by the K gene (or Kb) in the K series, as previously discussed, and that the agouti series comprises only the six alleles mentioned earlier.

Consequently, to determine the color configurations that can be produced by two German Shepherds, assuming the parents’ agouti alleles are known, we need only consider the agouti series itself.

Let us now examine the possible genetic configurations in detail.

A^wA^w Grey: it can only pass on the grey allele to offspring. Being the most dominant, it will always produce offspring with the grey phenotype.

A^wA^t  or A^wA^s  : Grey carrying black-and-tan; it can pass on either grey or black-and-tan. When mated with a black-and-tan or a grey carrying black-and-tan, it can produce both grey and black-and-tan offspring.

A^wa : Grey carrying black; it can pass on either grey or black. When mated with a black-and-tan, it can produce grey or black-and-tan offspring (since a is recessive to A^t and A^s , the offspring would be black-and-tan carrying black).

A^sA^s: Black-and-tan saddled,  it can only pass on the black-and-tan allele. When mated with a grey, it can produce grey offspring (or black-and-tan if the grey carries that allele); when mated with a solid black, it will only produce black-and-tan offspring (which can pass on the black allele).

A^sA^t: creeping tan ; it can only pass on the black-and-tan allele. When mated with a grey, it can produce grey offspring (or black-and-tan if the grey carries A^s or  A^t), when mated with a solid black, it will only produce black-and-tan offspring (which can pass on the black allele).

A^tA^t: Black-and-tan; it can only pass on the black-and-tan allele. When mated with a grey, it can produce grey offspring (or black-and-tan if the grey carries that allele); when mated with a solid black, it will only produce black-and-tan offspring (which can pass on the black allele).

A^ta: Black-and-tan carrying black. When mated with a black, a black-and-tan, or a grey that carries black, it can also produce black offspring.

aa: Recessive black, homozygous for the a allele. Can only pass a allele.

We must therefore always bear in mind that, as a dominance relationship A^y >A^ys > A^w > A^s= A^t >  a.

Punnett Square:
By knowing the parents’ genetic makeup, one can use a Punnett square to calculate the potential coat types of the offspring and their theoretical probabilities.

The Punnett square is used to calculate the possible combinations, and their associated theoretical probabilities—resulting from a mating with respect to a specific genetic trait. I say “theoretical probability” because, much like flipping a coin, the math might predict a 50/50 split (5 heads and 5 tails) over ten tosses, yet the actual observed results often differ. According to the law of large numbers, as the number of trials increases, the ratio moves closer to 50% heads and 50% tails; however, with just three tosses, it is not at all unlikely to get three heads. This is another reason why it is difficult to determine the genotype from the phenotype, even when the ancestry and offspring are known, unless the number of offspring is very large.

Example of a Punnett square for the mating of two homozygous greys.
Obviously, from two homozygous greys, we will get 100% homozygous grey offspring.

Example of a Punnett square for the mating of a grey carrying black with a black-and-tan carrying black. This case is more interesting and complex: theoretically, we will have:
25% grey offspring carrying black-and-tan
25% grey offspring carrying black
25% black-and-tan offspring carrying black
25% black offspring

to recap these are the possible genetic configurations of the alleles of the agouti series,

• A^w A^w
• A^w A^s
• A^w A^t
• A^w a
• A^s A^s
• A^s A^t
• A^s a
• A^t A^t
• A^t a
• a a

However, the two Black-and-Tan variants A^s (black saddled) and A^t (black-and-tan) exhibit incomplete dominance relative to one another and code for similar phenotypes. It would be too time-consuming to predict every combination by treating them separately; there are already so many possibilities. Since they behave identically regarding the wolf-grey (sable) phenotype which is dominant to black-and-tan and also regarding recessive black to which they are dominant. Let us examine the potential offspring from mating two dogs chosen from the three possible German Shepherd colors (grey, black-and-tan, and black). We can visualize this by constructing a Punnett square for each possible pairing, taking into account not only the dog’s visible color but also any alleles masked by the dominant one that could still be passed on to the puppies. Finally, we will briefly explain how the black-and-tan phenotype manifests depending on whether the A^s or A^t allele is present in the genotype.

Note for those with some knowledge of genetics:
Recent genetic studies on the Agouti locus (ASIP) indicate that the “saddle tan” pattern is not necessarily a distinct primary allele within the classical hierarchy; instead, it is often linked to genetic modifiers or structural variations (such as duplications or promoter changes) affecting the expression of the A^t allele. Nevertheless, in terms of practical inheritance and laboratory testing, the combination of these two traits continues to follow a pattern of incomplete dominance.

By taking two parents, each representing one of the possible combinations, and temporarily treating A^s and A^t as a single A^st  allele, we can calculate the theoretical outcomes of the mating.

Possible Agouti alleles couples are (A^w–A^w), (A^w–As^t), (A^w-a), (A^st–A^st), (A^st-a), (a-a)

• (A^w–A^w) (A^w–A^w) – 100% (A^w–A^w) Homozygous Grey
• (A^w–A^w)(A^w–A^st) – 50% (A^w–A^w) Homozygous Grey-50% (A^w–A^st) Greycarrying Black and Tan
• (A^w–A^w)(A^w-a) – 50% (A^w–A^w) Homozygous Grey- 50% (A^w -a) Greycarrying carrying recessive solid black
• (A^w–A^w)(A^st–A^st) – 100% (A^w–A^st) Greycarrying Black and Tan
• (A^w–A^w)(A^st-a) – 50% (A^w-At) Greycarrying Black and Tan – 50% (A^w-a) Greycarrying recessive solid black
• (A^w–A^w) (a-a) – 100% (A^w-a) Greycarrying recessive solid black
• (A^w–A^st)(A^w–A^st) – 25% (A^w–A^w) Homozygous Grey-25% (A^st–A^st) Black and Tan Homozygous – 50% (A^w–A^st) Greycarrying Black and Tan
• (A^w–A^st)(A^w-a)-25% (A^w–A^w) Homozygous Grey25% (A^w–A^st) Greycarrying Black and Tan – 25% (A^w-a) Grey carrying recessive solid black – 25% At a Black and Tan carrying recessive solid black
• (A^w–A^st)(A^st–A^st)-50% (A^w–A^st) Greycarrying Black and Tan – 50% (A^st–A^st) Homozygous Black and Tan
• (A^w–A^st)(A^st-a) – 25% (A^w–A^st) Greycarrying Black and Tan – 25% (A^w-a) Greycarrying recessive solid black 25% (A^st–A^st) Homozygous Black and Tan 25% (A^st-a) Black and Tan carrying recessive solid black
• (A^w–A^st)(a-a) – 50% (A^w-a) Greycarrying recessive solid black – 50% (A^st-a) Black and Tan carrying recessive solid black
• (A^w-a)(A^w-a) – 50% (A^w-a) Greycarrying recessive solid black 25% – (A^w–A^w) GreyHomozygous – 25% (a-a) Homozygous recessive solid black
• (A^w-a)(A^st–A^st) – 50% (A^w–A^st) Greycarrying Black and Tan – 50% (A^st-a) Black and Tan carrying recessive solid black
• (A^w-a)(A^st-a) – 25% (A^w–A^st) Greycarrying Black and Tan 25% (A^w-a) Greycarrying recessive solid black 25% (At-a) Black and Tan carrying recessive solid black 25% (a-a) Homozygous recessive solid black
• (A^w–a)(a-a) – 50% (A^w-a) Greycarrying recessive solid black 50% (a-a) Homozygous recessive solid black
• (A^st–A^st)(A^st–A^st) – 100% (A^st–A^st) Homozygous Black and Tan
• (A^st–A^st)(A^st-a) – 50% (A^st–A^st) Homozygous Black and Tan – 50% (A^st-a) Black and Tan carrying recessive solid black
• (A^st–A^st)(a-a) – 100% (A^st–a) Black and Tan carrying recessive solid black
• (A^st-a)(A^st–a) – 50% (A^st–a) Black and Tan carrying recessive solid black – 25% (A^st–A^st) Homozygous Black and Tan – 25% (a-a) Homozygous recessive solid black
• (A^st–a)(a–a) – 50% (A^st–a) Black and Tan carrying recessive solid black 50% (a–a) – Homozygous recessive solid black

Now, let’s suppose a black-and-tan puppy is born, just how extensive will the tan markings be?

This is with no doubt A^sA^s

Also this subject is  A^sA^s

So why, then, are the two previous dogs so different? Well, because there are other modifying factors that have been selected for in show lines specifically, a preference for that vivid red color and a saddle that extends back past the shoulders. These modifiers have become fixed in these lines; since they are quantitative traits, show lines can produce individuals ranging from the type shown above to ones that are almost entirely red with very little saddle.

This subject is A^tA^t

The dog shown below, on the other hand, is an A^sA^t  also known as “creeping tan” because the black extends to the shoulders and neck, even though it has receded compared to an  A^tA^t . In terms of color, this dog could easily be the offspring of the last two we just saw above.

This subject is A^sA^t  and is called Creeping Tan

This subject is A^w

The dog pictured up is an A^w(agouti) working-line German Shepherd; it is unknown whether it carries the black gene, the black-and-tan gene, or is homozygous for the grey (sable) gene. Analysis of color inheritance in German Shepherds reveals that color variation is influenced by various alleles interacting in complex ways. It is crucial to consider not only the visible phenotype but also the underlying genotypes that determine the different color expressions. Research continues to explore the relationship between genetics and morphological traits, thereby contributing to a deeper understanding of the breed. It appears that if an A^w dog carries the A^t or a allele, the black shading may be darker, however, modifying or quantitative factors—which have not yet been sequenced or cannot be detected via commercial tests also play a significant role here.

The subject below, on the other hand, is an A^w (Show line) and almost certainly carries A^s meaning it is A^wA^s.

Let us look at the difference in the extent of black/red banded hairs between the “show-line” grey dog ​​and the working-line dog mentioned earlier; we also note that the red on the former is much more vivid than the tan markings on the working dog. This is because breeding selection for the two lines has prioritized different traits: in the show line, the focus is on coat color specifically, achieving a color that adheres to a specific standard whereas in the working line, selection prioritizes dogs that excel at work. Consequently, color takes a back seat and tends to resemble the coloration of the earliest dogs selected shortly after the breed’s inception.

A brief, necessary mention of non-permitted colors follows.

There are two other genetic series that can influence the German Shepherd’s coat color: the D series (dilution) and the B series (brown), both of which can modify the dog’s color.

The D serie has two possible alleles: dominant D (non-diluted color) and recessive d (diluted color). Homozygous presence of the d allele slightly lightens the tan markings but, more importantly, turns black areas grey (blue) across the entire body, it affects the saddle and mask, as well as the black pigment in “grey” (sable) coats or solid black coats. The eyes turn amber, and the nose turns grey.

The B serie has two variants: dominant B (black) and recessive b (brown). Homozygous presence of the b allele turns black areas brown but has no effect on the fawn (tan) markings. As with the D series, this effect occurs across the entire body, affecting the saddle, the mask, and any black pigment in “grey” (sable) or solid black coats. The eyes turn amber, and the nose turns brown. If, by chance, the dog is homozygous for both d and b, the result is a lilac or isabella coat essentially a diluted liver color, all the black areas of the dog will take on this distinctive hue, which arises from the combination of the two recessive genes. The eyes turn amber and the nose becomes lilac.

Then there is another genetic series,

The E series (eumelanin mask), which in the German Shepherd should always carry the E^m value, includes:

Em: the black mask, the classic black mask found on German Shepherds, which can range from a faint trace around the lips to covering the entire face and ears, and even extending to parts of the legs (the latter being more commonly seen in the Belgian Malinois).

There are four other alleles in the E series: one found only in Cocker Spaniels and another only in Salukis and related breeds.

The other two are:

E: absence of a black mask with normal coat color (e.g., Collies).

e : recessive fawn.

If the e allele is present in a homozygous state (e e), the result is a cream/white dog, which is actually a very pale fawn, similar to a Yellow Labrador or a Golden Retriever.

This is the same color found in the White Swiss Shepherd, a breed now distinct from the German Shepherd and registered separately with its own standard, but it was once the color of perfectly normal German Shepherds, a trait that breeders attempted to eliminate during World War II.

When present in a homozygous state, this gene blocks eumelanin production in the coat but only in the coat, not in the mucous membranes, skin, eyes, lips, eyelid rims, etc. Consequently, the White Swiss Shepherd (or the white German Shepherd, if you prefer) must or at least should be well-pigmented, with a black nose and brown eyes; yet, there is no black hair in the coat itself it is entirely fawn-colored, including the whiskers, creating this distinctive look. The specific shade of fawn is determined by the “I” gene mentioned earlier.

Blue, liver, and fawn are all recessive traits, while they are undesirable and fall outside the breed standard, they persist in the breed’s gene pool. Because they are recessive, they can remain hidden for generations, only to reappear when two carrier parents happen to mate.

It was much easier, for instance, to eliminate the brindle pattern which, as we have seen, is dominant over non-brindle and was present in the breed early on. Eliminating a dominant trait simply requires avoiding the mating of dogs that display it. Eliminating a recessive trait from the gene pool, however, is far more difficult.

Consequently, blue, liver, or isabella German Shepherds are still occasionally born whether they would otherwise have been black-and-tan, solid black, wolf-grey, or white.

There is a circulating rumor that dilute colors particularly blue and isabella, and sometimes liver are associated with health problems. It is important to clarify that this is not the case; blue, liver, and isabella German Shepherds like the white ones are perfectly healthy.

There are breeds where the dilute or brown traits or even both combined are frequently (if not always) found, such as in the Weimaraner, we also see them in Collies (including Border Collies), Molossers (Mastiffs, Cane Corsos, Great Danes, etc.), and Bull-and-Terrier types (AmStaffs, Boston Terriers, etc.), and these are all healthy dogs.

In the Doberman, however, the dilute trait is associated with “color dilution alopecia” in 80% of cases, giving the dog a “mange-like” appearance.

It is worth noting that the genetic mutations responsible for these colors differ, even if the resulting effect is similar; for instance, the “brown” trait mentioned earlier exists in at least five different versions or distinguishable alleles that produce similar effects, even when paired heterogeneously (combining two of the five possibilities), with three of these appearing more frequently across various breeds. Consequently, it is entirely possible that the “blue” found in Dobermans is a different version of the blue found in other breeds, or that a specific gene absent in other breeds has become genetically fixed in Dobermans, causing coat issues only when the dilute trait is present. After all, while much of the dog’s DNA has been sequenced, the entire genome has not yet been mapped.

In any case, there are breeders in America selecting for German Shepherds in these non-standard colors; setting aside ethical debates and breed standards topics not covered in this article, which focuses solely on genetics—these dogs are perfectly healthy individuals.

Clearly, if a dog of this color were born, it should be placed as a pet rather than used for breeding; however, I certainly do not consider it ethical to euthanize them simply because they are the “wrong color” a practice that used to occur in the past and, regrettably, still happens today.

– Daniela Artioli