GENETICS

GENETICS OF THE BLUE WEIMARANER COAT COLOR

While there are many loci and alleles involved in the Weimaraner’s coat color (at least 10), there are only two loci that are important for the blue versus gray coat color in the Weimaraner, the Locus B pair and Locus D pair.  The B genes work in pairs, with one of each of these two alleles inherited from each parent. The D genes also work this way. Each of these genes may be dominant or recessive. Dominance is noted with a capital letter and recessives with a lowercase letter for that allele. In other words, B is dominant to b, and D is dominant to d. If present, the dominant gene will determine what you see and will always “override” the paired recessive.

Locus B Pair

The dominant B produces a black coat color whereas the recessive b produces a liver or chocolate coat color. Since these genes come in pairs, a dog could be BB, Bb or bb. BB individuals will be black. bb individuals will be chocolate. Bb individuals will also be black because the dominant B “masks” the b. The b is still there and can and does get passed onto the dog’s offspring, but it is not visible as the dogs phenotype (the physical characteristic that you can see). All Gray Weimaraners are bb. Blue Weimaraners are BB or Bb.

Locus D Pair

This pair controls dilution. The dominant D causes full pigmentation whereas the recessive d produces a dilute pigment. Because D is dominant, a Dd (or DD) individual will be fully pigmented and there would be no dilution of coat color.  It is commonly accepted that all Weimaraners are dd; that is, all Weimaraners coats are diluted and never fully pigmented. Thus, the dd dilution effect makes the bb chocolate/liver into the light tan that we call Weimaraner gray, and it makes Bb of BB black into a charcoal colored dog that we call Blue.

The dilution can work in degrees. In other words, it can make some dogs lighter than others. Some Blue Weimaraners can be so light as to appear gray. We must remember that the difference between blue and gray in Weimaraners is tonal, not the degree of dilution.  Thus a very diluted Blue can be much lighter than a Mouse-Gray, as can be seen in the top two photos to the right  More pictures of Ellie can be seen on her website.

When considering inheritance of coat color, we merely need to look at the locus B pair in Weimaraners since all Weimaraners are dd. A simple way to determine what a mating would produce is to do a Punnett square. With this tool we can predict the statistical outcome of genotype and phenotype. An empty Punnett square looks like this:


Empty Punnett square

First we would write down the genotype of each parent. Let’s say we are breeding a homozygous (having the same alleles, so BB) Blue Weimaraner to a Gray Weimaraner (bb). We would note one parents alleles on top and the other parents on the side. The empty squares represent the puppies. Since we know that each puppy inherits one of the alleles from each parent, we move one allele down into the offspring’s square.


How we fill in the squares

The completed Punnett square would appear like this:


A completed Punnett square of a monohybrid cross. Gray Weimaraner bred to a homozygous Blue Weimaraner.

As we can see from the completed Punnett square, a Gray Weimaraner bred to a homozygous Blue Weimaraner will produce 100% Blue Weimaraners, and further, all of them will be heterozygous Blues. In other words, all of the dogs will be blue and carry the gray recessive.

When we breed a Gray to a Blue who is carrying the recessive b, we can use the Punnett square to determine that we will statistically get 50% Blues and 50% Grays:


Gray Weimaraner bred to a heterozygous Blue Weimaraner

Thanks to this simple tool, it is now perfectly understandable how two Blues can produce Gray pups. Statistically we would see 75% Blues and 25% Grays:


Two Blues can produce Grays

Punnett squares only help predict probability and results are not statistically significant when dealing in small numbers. Therefore it would be theoretically possible for two Blues to produce an all Gray litter. However because Blue is dominant, it is never possible for two Grays to produce a single Blue in a litter.
 


       


RESOURCES

 
The Blue Weimaraner by Homer Carr
The Genetics of Weimaraner Coat Color by Ted Jarmie
    

LINKS
 
Genetics of Coat Color in Dogs - offsite
Canine Color Genetics - offsite
Weimaraner Coats by Jackie Isabell (About Longhairs) - offsite
    

PHOTO ILLUSTRATIONS

Click for larger image

A very dilute Blue, appearing deceptively lighter due to all the light in the photo.  Though she is light, the tone of her coat is still a diluted black rather than having any brown cast.  Note her nose color is also affected by the coat genes showing a dark gray nose. (Darker Blues have black noses.)

The same dog (left) next to her littermate, both Blues.

Photo of a Gray Weimaraner next to a Blue Weimaraner typical in coat color.  The Gray Weim is a dilute brown/chocolate, the Blue Weim is a dilute black.  Note the color of the noses compared to the nose of the light Blue Weim in the first picture.

 

 
 
 
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