genetic colour transmission in German Shepherd dog
If you talk about German Shepherd, people imagine a classical black and tan “saddled” dog, usually a “show type” one, because of it is the most common German Shepherd dog colour and type, but we know it’s not the only possible colour in our breed. If we walk around with a total black or a sable German Shepherd dog, people often ask if it’s a mix breed dog, or, for example, they think it’s another breed, such as Groenendael Belgian Shepherd Dog for total black dogs. But German Shepherd lovers knows there are 3 different accepted colours in German Shepherd dog genetic. Or, we better say there are 3 different colours, but with modifier genes, not all sequenced yet, that can change a lot the final “layout” of the dog itself.
Before we speak about the genetic colour transmission of German Shepherd dog , we must write a little introduction about genetic, for better understand the rest of the article. All the “information” regarding a living creature it’s written in “DNA“, a sort of “double chain” with a lot of “couples of genes”, all these couples contains information about all the “details” of the subject, and the 2 genes in a couple are redundant , one is passed from mother and one from father and both describes a single physical characteristics about the subject. Dogs has 78 (39 couples of) chromosomes and each chromosome contains a certain number of genes, each gene, or set of more than one genes, describe a characteristic about the subject, and this comprehends also character, behaviour, growth rhythm and so on. The “values” a gene can assume are called “alleles“, usually we ave from 2 to 5 possible different alleles for a gene , but it’s not impossible we have more than 5 or sometimes only one possible allele.
A gene and it’s possible alleles are called “series”
the position of a gene into the DNA chain it’s called “locus” (singular), “loci” (plural)
What we will see “outside” looking or doing Clinical examinations to a subject it’s called
“phenotype”, what we have “written inside” DNA it’s called “genotype“.
Phenotype it’s always a combination of dominance rules between genes (alleles) and what append to the subject in the place he grows and lives during ontogeny. so, if we look to the subject from outside, it’s not always so easy to understand which values we have in a couple of genes . We must do a genetic DNA TEST, when possible to know it for sure, and we say when it’s possible because of not all genes have been identified and studied yet.
We know there are dominance rules between alleles.
If both alleles in a series are identical, we speak about “Homozygous“, and there is no doubt about phenotype, we see what both identical genes in the series describes. But, if genes are not identical, when we have 2 different alleles in the couple, we speak about “Heterozygous“, so, in these case, we have “dominance rules” between different alleles, and what we see outside in the phenotype is determined by those rules.
We have several dominance rules type, we explain the more interesting for this article. if the “dominance” of one allele against the recessive one it’s “complete” only the dominant one of these alleles is expressed, so the subject looks like alleles are both of the dominant value in the DNA, when dominance it’s “incomplete” the phenotype is an intermediate type between the two homozygous phenotypes, if we have “co-dominance” both phenotypes are full expressed like in the separated homozygous cases (like blood type, that can be A, B or AB).
Dominant alleles are generally written with a capital letter, for example B. Recessive alleles are written with a lower case letter, for example b,if we have more than two possible alleles for a series, we have a sort of chart, from more dominant to less dominant values. We can write… A1>A2>A3…>an where A1 it’s the more dominant allele and an the less dominant. If we take 2 allele from this series, the left one value in the chart it’s dominating all values on his right.
Well, it’s time to speak about some genetic series yet sequenced and with a suitable test, useful to clearly identify genotype, because, as we told before, it’s not always possible to know genotype by only looking to dog’s parents/sons and dog’s phenotype.
The K Series:
Dominant black it’s very common in a lot of breeds, like for ex Groenendael Belgian shepherd Dog, Labrador Retriever, black and white Border Collies and so on, but not in German Shepherd dog, where we have a recessive version of solid black, caused by another series, called Agouti series. Agouti is the main series we have to look at, to understand transmission of colour in our breed. Dominant black, by the way, is caused by K series, where we have 3 alleles:
K (upper case) the top dominant, we only need one allele in the couple with K value to get solid black dogs
Kbr, for Brindle, we need 2 Kbr or a Kbr and a k (lower case) to get brindled dogs
k (lower case) it’s the less dominant allele, and we need 2 k alleles in the couple to see the effect of the Agouti series upon our dog.
Kbr too let us see Agouti series effect, but with a sort of “black grid” upon the dog, so where the dog is black we obviously see no effects, where the dog it’s fawn, wee see a striped fawn zone… Brindled boxer it’s a typical example of total dominant fawn dog but with a grid upon it than let us see black striped fawn zone, and in boxer the fawn zone it’s “all the dog”, so the dog it’s all brindled. In German Shepherd dog, we ALWAYS have (k-k), the less dominant allele in Homozygous form, even if it seem there are some subjects with one or two K (upper case) in the K series (dominant black) but it’s not the more common form of solid black for German Shepherd. In Belgian Shepherd dogs, for example, we have (K-K) or (K-k) in Groenendael, and kk in fawn dogs such as Malinois, Tervueren and Leknois.
The Agouti series:
let’s now got to explain Agouti series and his 4 alleles.
The more dominant allele it’s Ay, where A stands for Agouti and y for yellow
Ay – Dominant Fawn
This it’s the dominant fawn allele, we need at least one allele with this value in the Agouti series,to get dogs looking like fawn Great Dane, fawn Pug or Tervueren and so on. This allele it’s not anymore present in German Shepherd, because of it is very easy to eliminate a not wanted allele from a series when it’s the dominant one, we only need to not reproduce fawn dogs and we will loose the Ay allele in the breed forever. By the way, a recessive allele can be hidden for generations and generations so we can get recessive colours on pups after a lot of generations when, for a case, two alleles of this type combine together. So, now we can understand why, usually mix-breed dogs born total black or fawn, because those are the two most dominant colours. Solid black from K series, or fawn in Agouti series in case K series has kk alleles couple.
the second allele in order of dominance, after Ay is Aw, where w stands from wild. It’s the grey, or sable one, the most common colour for working German Shepherd Dogs. It’s the colour of the wolf, with some modifiers genes, but it’s the same colour, and this allele is present in a lot of wild animalsbecause of it’s the most mimetic colour in a forest.At-Tan points After Aw, we have
At-Tan Point, where t standing for tan points, it’s the classic black and tan saddled German Shepherd Dog. Even if it seems we have different types of black and tan, from “Dobermann-like” black and tan to an almost all fawn black and tan dog, in the Agouti series it’s always an (At-At ) or (At-a) (a it’s the recessive black, we will soon look to). We will back to this allele after, to better explain it.
And at last we have our recessive black allele:
a-recessive solid black
We need two a allele to have recessive solid black German Shepherd… and the phenotype it’s not different from K dominant black one, so only with a DNA test we can understand and be sure if a total black dog it’s black for a K gene in the k series or an (a-a) couple in the Agouti series with (k-k) in the K series. And it can be both, (K-K) (a-a) or (K-k) (a-a), but with a upper case K in the k series total black it’s caused by K even if the dog can pass recessive black to his pups.
(K-k)dog can generate all possible colours, if we breed two (K-k) black dogs, (k-k)(a-a) dogs can only generate (k-k)(a-a) black dogs if we breed two (k-k)(a-a)black dogs.
Let’s now turn back to the most German Shepherd’s colour, Black and tan saddled. Until Agouti series have not been full sequenced, the saddled allele it was supposed to be distinct from the black and tan “dobermann-like” one. Now we know it’s not so. There are only one black and tan allele in the Agouti series and other modifier genes, not all sequenced yet, deciding how much tan expands from when the dog born. As we all have seen German Shepherd Dog pups, we know they all born almost black with little tan points, upon eyes, at the side of the muzzle, on the back of tail and on paws/lower side of legs… and while the dogs grows up, those points expand and it remains only a black saddle and a black, muzzle or sometimes a little stripe on the backbone. If we cross an almost black dog with a clear dog, with only a little black stripe on the backbone, we got pups with an intermediate saddle, varying from most saddled to less saddle between parents range, with tendencies to a middle saddle extension. Even fawn colour are always genetically the same fawn, even if it seems it can be so different between subjects, fawn is varying from almost white or white looking (because of the too few pigment ion the hair) to a strong red. Fawn colour it’s caused by Pheomelanin, the red pigment, and Eumelanin causes the black pigment in the hairs. But we have other modifier genes, that can affect those two pigments on the hair of the dog, and in the case of black and tan, we can consider the I gene, where I stands for intensity and it affects fawn only, clearer fawn has less pigment and vice versa, and it’s decided by the allele in the I loci. Unfortunately I has not been sequenced yet.
By the way, even in total fawn dogs (like Belgian Shepherds) or sable dogs, I allele affects fawn intensity. So it doesn’t matter what we found in Agouti allele, we will have clearer ormore reddish fawn in dogs depending on I gene.
once time even dominant black allele, was supposed to be an Agouti allele, then after discovering K series and sequencing all Agouti series Alleles, geneticists realized it was not so, and dominant black has another loci. The K loci.
We do not have a dominant black allele in Agouti series!
Well, if we want to forecast possible pups colour out of a litter, we must consider only parent’s Agouti alleles, then fawn intensity and extension will probably be a intermediate between parents values like wrote before.
Let’s now see wich Agouti alleles combinations are possible in German Shepherd dogs
Aw-Aw – Sable (Grey) the dog it’s sable and can only pass sable to offspring, and offspring will always be sable in the phenotype.
Aw-At – Sable (Grey) carrying black and tan. it can pass both sable or black and tan alleles to the offspring. If crossed with a same Agouti allele combination dog, we can have sable or black and tan pups
Aw-a – Sable (Grey) carrying recessive black. It can pass both sable or recessive black alleles to the offspring. If crossed with a same Agouti allele combination dog we can have sable or black and tan. If we cross it with a black and tan dog we can obtain sable, black and tan or a total black if the black and tan carries recessive black too. Black and tan Pups from this combinations will be surely black and tan carrying recessive black.
At-At – back and tan. It can only pass black and tan allele to offspring. Crossed with a sable one, it will born out sable pups or even black and tan if the sable it’s carrying black and tan. Crossing it with a recessive solid black, we will obtain only black and tan dogs carrying recessive solid black.
At-a – Black and tan carrying recessive black. If crossed with black and tan or sable both carrying recessive solid black, we will have black and tan sable or recessive solid black.
a-a recessive solid black, Dog can only pass recessive solid black allele to offspring. Crossing two solid recessive solid black dog we will have only total recessive black offspring.
We only explained some combinations and offspring but, we have a lot more, and we soon will write all. But we always have to take in mind this dominance chart: Ay>Aw>at>a.
Once we knew what alleles are present in parent’s Agouti series, we will calculate possible offspring colour type and theoretical probability % score, using the “Punnet Square”.
We speak about theoretical probability % score, because if for example we flip a coin 2 times, it’s not impossible we will have 2 heads, but theoretically we must get one and one… with a few event, what comes out it’s not obvious it will follow theoretical probability % score. As much as we increase event number, as much as scores will reach values similar to theoretical scores. And, this is another reason why it is not easy to understand what we have in genotype looking parents and offspring.
Punnet Square example.
Crossing two Homozygous sable dogs. we will always get 100% Homozygous sable offspring
Another Punnet Square example. Crossing sable carrying black and tan with black and tan carrying recessive solid black. This is a more complicate and interesting case, we will get:
25% sable carrying black and tan
25% sable carrying recessive solid black
25% black and tan carrying recessive solid black
25% recessive solid black
Well, now we know how to calculate offspring colours theoretical probability % score while we know all the possible allele couples for Agouti series, we can built up a punnet square for each allele pair combination to see what theoretical can come out in the litter.
Possible Agouti alleles couples are (Aw-Aw), (Aw-At), (Aw-a), (At-At), (At-a), (a-a)
- (Aw-Aw) (Aw-Aw) -100% (Aw-Aw) Sable
- (Aw-Aw)(Aw-At) – 50% (Aw-Aw) Homozygous Sable – 50% (Aw-At) Sable carrying Black and Tan
- (Aw-Aw)(Aw-a) – 50% (Aw-Aw) Homozygous Sable – 50% (Aw-a) Sable carrying carrying recessive solid black
- (Aw-Aw)(At-At) – 100% (Aw-At) Sable carrying Black and Tan
- (Aw-Aw)(At-a) – 50% (Aw-At) Sable carrying Black and Tan – 50% (Aw-a) Sable carrying recessive solid black
- (Aw-Aw) (a-a) – 100% (Aw-a) Sable carrying recessive solid black
- (Aw-At)(Aw-At) – 25% (Aw-Aw) Homozygous Sable – 25% (At-At) Black and Tan Homozygous – 50% (Aw-At) Sable carrying Black and Tan
- (Aw-At)(Aw-a) – 25% (Aw-Aw) Homozygous Sable 25% (Aw-At)Sable carrying Black and Tan – 25% (Aw-a) Sable carrying recessive solid black 25% At a Black and Tan carrying recessive solid black
- (Aw-At)(At-At) – 50% (Aw-At) Sable carrying Black and Tan – 50% (At-At) Homozygous Black and Tan
- (Aw-At)(At-a) – 25% (Aw-At) Sable carrying Black and Tan – 25% (Aw-a) Sable carrying recessive solid black 25% (At-At) Homozygous Black and Tan 25% (At-a) Black and Tan carrying recessive solid black
- (Aw-At)(a-a) – 50% (Aw-a) Sable carrying recessive solid black – 50% (At-a) Black and Tan carrying recessive solid black
- (Aw-a)(Aw-a) – 50% (Aw-a) Sable carrying recessive solid black 25% – (Aw-Aw) Sable Homozygous – 25% (a-a) Homozygous recessive solid black
- (Aw-a)(At-At) – 50% (Aw-At) Sable carrying Black and Tan – 50% (At-a) Black and Tan carrying recessive solid black
- (Aw-a)(At-a) – 25% (Aw-At) Sable carrying Black and Tan 25% (Aw-a) Sable carrying recessive solid black 25% (At-a) Black and Tan carrying recessive solid black 25% (a-a) Homozygous recessive solid black
- (Aw-a)(a-a) – 50% (Aw-a) Sable carrying recessive solid black 50% (a-a) Homozygous recessive solid black
- (At-At)(At-At) – 100% (At-At) Homozygous Black and Tan
- (At-At)(At-a) – 50% (At-At) Homozygous Black and Tan – 50% (At-a) Black and Tan carrying recessive solid black
- (At-At)(a-a) – 100% (At-a) Black and Tan carrying recessive solid black
- (At-a)(At-a) – 50% (At-a) Black and Tan carrying recessive solid black – 25% (At-At) Homozygous Black and Tan – 25% (a-a) Homozygous recessive solid black
- (At-a)(a-a) – 50% (At-a) Black and Tan carrying recessive solid black 50% (a-a) – Homozygous recessive solid black
Let’s now speak a little about not recognized German Shepherd colours.
We have two other series affecting dog colours, D for dilution and B for black-brown.
The D series
in D series the dominant allele is D, if we have (D-D) or (D-d) alleles couple in the dilution series, fawn of black are not affected by this gene, but if we have an Homozygous d, Black will turn in blu, all the black pigment upon dog, wherever we may find it, even skin and nose, will turn from black to blue, and fawn will look a little clearer. This gene affects both red and black pigment type, but it’s more evident on black one.”Diluted” dogs has amber eyes
The B series
B series only affects black pigment. The dominant allele is B, if we have (B-B) or (B-b) alleles couple in the Brown series, black is not affected by this gene, but if we have an Homozygous b, Black will turn in brown, also called liver, all the black pigment of the dog wherever we may find it, even skin and nose, will turn from black to Brown.
“Liver” dogs has amber eyes.
If we both find (b-b) and (d-d) liver will turn in to Lilac, also nose and skin, eyes are always
The E series
Another dog colour’s series is the E series, in E series we have 5 alleles, where one it’s found only in Cocker spaniel, and another only in Saluki and similar dogs, but we have Em, E and e as possible alleles e in a lot of dog breeds.
Em is the top dominant, and it’s the “black muzzle” allele, almost all German Shepherd today have homozygous Em, and it must be so. The black muzzle can cover muzzle from a little black stripe around lips to an all black face, covering sometimes also chest and legs like in some Belgian Malinois.
E is the second allele in dominance chart, and it let the Agouti series come out but without
black muzzle (ex collies).
e is the less dominant one, the “recessive fawn” allele.
When two e meets, in an e homozygous dog, we will not have black pigment on the hair of the dog. This combinations inhibits production of black Colour in the hairs and only hairs, not in skin nose or eyes. All Hairs will turn in fawn. How much “fawn” it will depends always from I gene, as we have seen before. Well, this is the combination causing White Swiss Shepherd colour, once present in German Shepherd dogs, because of Greif, Horand’s Grand dad, was an (e-e), recessive fawn dog, and now almost disappeared, even if sometimes a “white” pup will born from 2 coloured dogs. for this reason, crossing a white Shepherd with a coloured shepherd one, will almost never generate white pups, it will append only of the coloured one carries e in E series. This is also the Golden retriever, yellow labrador retriever colour (with different I value), or Samoyed, Italian “Maremmano” dog or so on.
Well, both d, b and e, even if are not appreciated, are still in the German Shepherd dog genome and sometimes liver, blue, Lilac or recessive fawn (white) dogs can born. As we told before it’s not easy to remove recessive alleles because they can not come out for a lot of generations until one dog carrying it meets another one. And, as it’s only a colour problem, it doesn’t make sense to not reproduce a possible carrier of one of these 3 recessive alleles if the dog is a good and healthy dog. it’s more easier to take away dominant alleles, like brindle one (Kbr), once present and now disappeared in the breed.
People talk about diluted colour health problems, but it’s not so. Diluted dogs are healthy
dogs, only not appreciated.
In some breeds such as dobermann, 80% of diluted dogs are affected by colour dilution alopecia, this can be true, probably diluted allele it’s associated with another allele, or it’s a different allele because of mutations sometimes comes out, and we can get not identical but with similar effects mutations. For ex. we have 3 different distinct b (brown) alleles, with similar effect, in combined together they produce liver dogs even if we have 2 different b allele type. By the way we have also diluted healthy breeds such as Weimaraner (always blu/lilac) , a lot of pit bull and Amstaff are blue and not only… and they all are healthy.
So, it doesn’t make sense to put to sleep unwanted colour pups, as they are normal and healthy dogs!