The genetic colour transmission in German Shepherd dog
GENETIC
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 "informations" 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 informations 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 allele.
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 animore 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.
aʷ-Sable
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 animals
because of it's the most mimetic colour in a forest.
aᵗ -Tan points
After aʷ, we have aᵗ , with 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 aᵗa (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 aa couple in the Agouti series with (k-k) in the K series.
And it can be both, (K-K) aa or (K-k) aa ,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) aa dogs can only generate (k-k) aa black dogs if we breed two (k-k) aa 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 expandes 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 or
more 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
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aʷaʷ - Sable (Grey) the dog it's sable and can only pass sable to offspring, and offspring will
always be sable in the phenotype.
aʷaᵗ - 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
aʷa - 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.
aᵗaᵗ - black 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.
aᵗa - 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.
aa 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 aʷaʷ aʷaᵗ aʷa aᵗaᵗ aᵗa aa
aʷaʷ x aʷaʷ = 100% aʷaʷ Sable
aʷaʷ x aʷaᵗ = 50% aʷaʷ Homozygous Sable - 50% aʷaᵗ Sable carrying Black and Tan
aʷaʷ x aʷa = 50% aʷaʷ Homozygous Sable - 50% aʷa Sable carrying carrying recessive solid black
aʷaʷ x aᵗaᵗ = 100% aʷaᵗ Sable carrying Black and Tan
aʷaʷ x aᵗa = 50% aʷaᵗ Sable carrying Black and Tan - 50% aʷa Sable carrying recessive solid black
aʷaʷ x aa = 100% aʷa Sable carrying recessive solid black
aʷaᵗ x aʷaᵗ = 25% aʷaʷ Homozygous Sable - 25% aᵗaᵗ Black and Tan Homozygous - 50% aʷaᵗ Sable carrying Black and Tan
aʷaᵗ x aʷa = 25% aʷaʷ Homozygous Sable - 25% aʷaᵗ Sable carrying Black and Tan - 25% aʷa Sable carrying recessive solid black - 25% aᵗa Black and Tan carrying recessive solid black
aʷaᵗ x aᵗaᵗ = 50% aʷaᵗ Sable carrying Black and Tan - 50% aᵗaᵗ Homozygous Black and Tan
aʷaᵗ x aᵗa = 25% aʷaᵗ Sable carrying Black and Tan - 25% aʷa Sable carrying recessive solid black 25% aᵗaᵗ Homozygous Black and Tan 25% aᵗa Black and Tan carrying recessive solid black
aʷaᵗ x aa = 50% aʷa Sable carrying recessive solid black - 50% aᵗa Black and Tan carrying recessive solid black
aʷa x aʷa = 50% aʷa Sable carrying recessive solid black - 25% aʷaʷ Sable Homozygous - 25% aa Homozygous recessive solid black
aʷa x aᵗaᵗ = 50% aʷaᵗ Sable carrying Black and Tan - 50% aᵗa Black and Tan carrying recessive solid black
aʷa x aᵗa = 25% aʷaᵗ Sable carrying Black and Tan - 25% aʷa Sable carrying recessive solid black -25% aᵗa Black and Tan carrying recessive solid black - 25% aa Homozygous recessive solid black
aʷa x aa = 50% aʷa Sable carrying recessive solid black - 50% aa Homozygous recessive solid black
aᵗaᵗ x aᵗaᵗ = 100% aᵗaᵗ Homozygous Black and Tan
aᵗaᵗ x aᵗa = 50% aᵗaᵗ Homozygous Black and Tan - 50% aᵗa Black and Tan carrying recessive solid black
aᵗaᵗ x aa = 100% aᵗa Black and Tan carrying recessive solid black
aᵗa x aᵗa = 50% aᵗa Black and Tan carrying recessive solid black -25% aᵗaᵗ Homozygous Black and Tan - 25% aa Homozygous recessive solid black
aᵗa x aa = 50% aᵗa Black and Tan carrying recessive solid black - 50% aa Homozygous recessive solid black
aa x aa = 100% aa Homozygous recessive solid black
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The problem of the dominant black.
It has become part of the genetic heritage in recent years, a gene that was not previously present in the German shepherd, or K (uppercase).
Allele of the series called K.
Until now in the German Shepherd all the subjects had two copies of k (minuscule) or in homozigosi, and only this genetic combination makes it possible to manifest on the mantle of the classic colors that we know of the German shepherd, namely wolf gray and black focato, and of course, also recessive black, only that that is not distinguishable from the dominant black, which is precisely the effect that produces the presence of even a K (Shift) in the locus. For this reason in recent years it is surprising that from two black subjects, non-black puppies can also be born, when it was once known to be impossible.
The presence of the allele K (uppercase) prevents the expression of the genes of the series sharp on the phenotype, the Aguti series is the one where the alleles are located that tell us what color our German shepherd is, in a dominant black subject so, in the series Aguti can be anything, it is not given to see it. This effect, that is, the non-expression of a gene on the phenotype, therefore in the presence of another gene in another genetic series is called EPISTASI.
But the genes in the "hidden" series, therefore, are transmitted in the same way from parents to children, they simply do not express their effect on the subject's mantle as they should. There are, but they are not seen, in a few words.
So, if the dominant black subject has only a capital K, statistically 50% of the puppies inherit from this parent the lowercase k, and so the color of the puppy will follow the pattern of the color inheritance of the German Shepherd that we are used to seeing.
The other parent can be equal requirements, with a capital K, as can be a German shepherd "classic" with two lowercase k.
so let's put down a pattern to calculate these cases as well.
KK homozygous dominant Kk heterozygote 50% dominant kk homozigous can enclose all colors and follow the classic pattern taking into account the locus at
Whenever one or two K (capitals )are present in the genotype, the blak phenotype is dominant
kk x kk - 100% kk (classic color scheme)
Kk x kk 50% kk probability of you inherit k (classic color scheme)
50% Kk probability of inheriting K (dominant black)
Kk x Kk - 25 KK % likely to inherit K from both (dominant black)
25% kk probability that you will inherit k from both (classic color scheme)
50% Kk probability of inheriting K from one parent k from the other (dominant black)
KK x kk - all puppies are dominant blacks (but all bearers of dominant non-black -> Kk)
KK x Kk - all puppies are dominant blacks
(50% probability of dominant non-black carriers -> Kk)
KK x KK - 100% KK All puppies are dominant blacks and can only generate dominant black puppies
The dominant Blacks anyway in the sharp series we always have a combination that follows the classic pattern, but it is not given to see it.
Therefore, for not having surprises, the only thing to do is to test the K series and the Aguti series (A) and see what our dogs bring.
I remember that a dominant black, so the presence of one or two K in the K series is all black regardless of what's in the sharp series and that a dominant black with any genetic combination in series A and series K is Indistinguishable phenotypicically (i.e. with the naked eye) from a kkaa or a recessive black generated by the agouti series, that is, the old solid black of the German shepherd that we have had until now, the "classic".
That's why sometimes two blacks don't just get black puppies like we used to be.
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Daniela Artioli
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
amber.
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 “;aremmano” 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!
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