Posted: Sun Apr 13, 2008 12:55 pm Post subject: Variations in coat colours
So far, we have only looked at inheritance by a single gene at the B locus.
In reality more than one gene locus is involved in the inheritance of coat
colour. A second locus, found on a different chromosome, the E locus, has to
be present in its dominant form if any colour is to be expressed. This
interaction between different loci on different chromosomes is known as
epistasis. Therefore, a dog carrying the genotype EE or Ee for the E locus
will be able to produce a colour pigment. This locus now interacts with the
B locus i.e. black colour is inherited by the genotypes EEBB, EEBb, EeBB or
EeBb. Brown colour in GLP's, is inherited by the genotypes EEbb or Eebb.
If there is no dominant allele for the E locus i.e. ee then the colour will
be red, as in the Irish setter, or yellow. This is an example of the E locus
being epistatic to the B locus. When the E locus is recessive {ee} then the
B locus cannot be expressed and a colour other than black or brown is
produced.
We are now in a position to look more closely into the inheritance of coat
colour in the GLP. Before looking at each gene in turn we need to know that
mammals including dogs have two forms of melanin in their coats. Let us look
at each of the genes separately, starting with the gene at the E locus. This
gene is the Melanocyte Stimulating Hormone Receptor Gene and is responsible
for the production of eumelanin pigment. An EE or Ee genotype produces a
dark colour either black or brown in gundogs. The ee genotype can only
manufacture the other form of pigment called phaeomelanin producing red or
yellow colouration. Therefore, all GLP's must be EE, Ee is a possibility but
this would lead to red or yellow coat colour for 25% of the offspring
this was taken from Coat colours in the GLP by Robert Simpson found on our website.
GLP's must be EE homozygous dominant, otherwise ALL litters of GLP's would contain 25 % red/ yellow
Breeds which are homozygous recessive include English and Red setters.
In some countries GLP litters now have yellows which means homozygous ee must have been introduced in their pedigree.Included in this litter were 2 all whites born dead.
Click to see full size image
Gosh how interesting. I wonder where the yellow comes from then?? I suppose the solid pattern will come from the pattern gene rather than the colour gene such as the GWP? _________________ Sharon Pinkerton
www.bareve.com
Owner & breeder of Field Trial 1st prize winners
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The coat colour in the the GLP can be suggested as kk ( long coat ) EE
( expression of coat colour brown ) bb ( brown ) Ss ( solid colour )
Tt ( ticking gene ) ie kkEEbbSsTt.
The yellow colour cannot be expressed by " chance " or mutation of a gene as coat colour involves more than one gene locust.
The yellow puppies in the picture must be ee recessive but Longhairs are homozygous dominant EE. The ONLY way to alter this is by introducing recessive ee which introduces heterozygosity, this can only occur with bloodlines that are not GLP's.
EE brown Ee Brown ee all yellow or white
Breeds which are homozygous ee are English and Irish setters.
This is not a first time occurance, all whites have been bred in Ireland but they have the lethal and semi lethal gene because they die at birth of while very young. I have spoken to a man who owned one.
Annie informs me some Irish setter blood was experimented with in the 1800's but of course this introduced red dogs, yellow dogs and white dogs so this soon stopped with culling.None of the 5 foundation dogs contained ANY setter blood.
In the 1990's litters were being born not to correct colour standards. To deny no involvment with other bloodlines is not genetically possible.
The Germans of course stick to what they do best, maintaining type so this just does not happen over there.
This is what happens when owners want to change breeds to make them go faster or smaller or prettier or tri- coloured, bi-coloured or not coloured at all. nature intervenes then with lethal or semi lethal genes and who want to introduce those into breeds.
Can anyone tell me the logic of basing a tri-coloured pattern [as in the tri-colour brittany] on a bi-colour [as in the Gordon Setter]
This was put forward because the markings on the Gordon Setter are in the right place for a tri _________________ Jan
Ghillie, hips 8/9=17 and Merlin, hips 9/9=18 My opinions are brilliant, intelligent [sometimes] and MINE alone! If you want one I can give it to you. Sean Bean has wrinkles just like Bill!!!
The Gordon Setter was originally a tri white , black and tan.
If you look at the Trueman's Assarts working Gordon's they all had a lot of white. This I would presume came from their original old setter background. ( Is this correct Sharon ? )Most working Gordons trialling in the 80's were tri's.
I once looked at a picture painted by Wilkinson, in the gallery it was down as an English, if fact if you looked at it's head shape it was a Gordon. I'm pleased to say the gallery owner changed it.
As for colour coat definitions in Brits, sorry don't have a clue but if you write down standard colours it can be worked out, have you not had definitions of colour and their transference worked out for your breed?
This does make proposed matings much easier for me when I have schimmels and solids, I know what I'm going to get.
There has been a proposal to change the wording of the Brittany standard regarding the orange markings on the tri-colours ie; eyebrows, legs, cheeks and under the tail [in other words the same or similar to most tri's] However the people putting forward the proposed change want it based on the Gordon Setter black and tan markings. Just seemed to be a little strang to use a bi-colour dog as the example instead of another tri.
There is not a lot we can say, as this has now gone forward to the KC for their consideration, other than to wonder at the way some people's minds work. The people concerned want the markings to be much more precise This, despite the fact that in many other breeds, people have been trying for years to get markings exactly where they are wanted _________________ Jan
Ghillie, hips 8/9=17 and Merlin, hips 9/9=18 My opinions are brilliant, intelligent [sometimes] and MINE alone! If you want one I can give it to you. Sean Bean has wrinkles just like Bill!!!
Nobody seems to know. The persons who got it put through the AGM have only ever bred the basic orange and white versions of our breed to my knowledge. So I don't really know what knowledge base they were using as all they said was - 'similar to Gordon Setter' and unfortunately no-one, including myself, picked up on it. But the FCI standard does mention tricolour markings but not as specific as was put through. I believe this was changed fairly recently by the French Committee. I have been led to believe that genetically it is difficult to produce exact patterns with three colours - is this true?
BA
_________________ Aberdon HPR's. Good-looking AND Intelligent.
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