The following is from a science student on another board. White Dobermans are albino. Period. They are not the same thing as an Isabella. (fawn) They have much, much higher incidence of health and temperament problems than other Dobes and should NOT be bred.
The DPCA also provides a nice chart of color inheritance in the doberman (found here:
http://www.dpca.org/color.chart.5.html).
The basics of genetics:
There are various different forms of each gene in any animal's genome - the different forms of the gene are called alleles. Each animal (or person) has two copies of every gene they posses -- one from their mother and one from their father.
In the most simple case of Mendelian genetics, a gene will only have two different alleles present in the gene pool (things such as height which show a large variation, have many alleles) -- one dominant and one recessive. Dominant alleles are usually represented by capital letters and recessive alleles are usually represented by lower case letters. In the case of a copy of both the dominant and recessive allele being present in the animal (called heterozygous; homozygous is having two copies of the same allele), the recessive allele will usually be "silent" and only the dominant allele will be expressed in the animal's phenotype (how the animal looks).
In the doberman, there are two genes that interact to determine coat color -- B/b and D/d. When a dog is dominant for both of these genes (either homozygous dominant or heterozygous), he is black. When a dog is dominant for the B gene (either homozygous or heterozygous = BB or Bb) and recessive for the D gene (homozygous only = dd), he will be blue. When a dog is recessive for the B gene (bb) but dominant for the D gene (DD or Dd), he will be red. When a dog is recessive for BOTH genes (bbdd), he will be fawn.
Thus, when you determine all the possible combinations these alleles of these genes (see the DPCA chart, that is what they have done), you will see that there are only FOUR phenotypic possibilities.
As I explained above, when only the recessive alleles of one or both these genes is present, the color of the dog changes. Thus, having two recessive alleles for one of the genes (either B_dd or bbD_) would be a single dilution (red or blue) and having the two recessive alleles for both of the genes (bbdd) would be a double dilution.
The albino gene (C) is present in all dobermans determines whether or not color is expressed. From the patterns of inheritance observed from the breedings of the original albino bitch, it was determined that the condition of being albino was inherited in an autosomal recessive fashion. Thus, to be an albino, you must have two copies of the recessive allele (cc). Dogs that are not albino and do not carry the albino gene are homozygous dominant (CC). Dogs that are not albino but *carry* the gene, the z-factored dogs mentioned above are heterozygous (Cc). Thus, if two z-factor dogs are bred together (Cc x Cc), each parent can either donate a dominant or a recessive allele to the offspring. Thus, 3/4 of the dogs from this breeding would be express the color coded for by their B and D genes (25% would be genotypically CC and 50% would be genotypically Cc) and 1/4 of the dogs would be albino (25% would be cc).
In other words, if there is even one dominant copy of the albino gene, the dog will express color. If there are no dominant copies (homozygous recessive = cc), the dog will not express color.
Now, the statement that the albino gene is not related to the dilution genes from the DPCA should make more sense. The B and D genes can code for any of of the four colors -- if there is a dominant copy of C present, then the color coded for by the B and D genes will be expressed. If there is no dominant copy of c present, no pigment will be expressed, thus, it does not matter which alleles the dog contains for the B and D genes because no color is being expressed.
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Now that I have gotten through the basics, I will examine the claim made in this thread that there is a genetic difference between "white" dobermans and "albino" dobermans.
The claim was that "white" is not albino, but a dilution of fawn. This would mean the dog would still express pigment (be dominant for the albino gene), but there is somehow a third gene that determines coat color that is present in the recessive form.
Now, I'll be the first to admit here that I'm by far not a genetics expert. I am an undergraduate biology major with little experience in dog genetics... but, this just doesn't make sense to me.
Based on basic Mendelian principles, if there was three genes that determined coat color, there would not just be five possible colors (black, blue, red, fawn, and white)... there should be... well, a lot more! With two genes that code for color, there are 9 different genotypic possible combinations and 4 different phenotypic possibilities... I mean, having a third gene that would have and influence on ONE form of the B and D genes (fawn, bbdd)... would be pretty unlikely... it would have to have an impact of all 9 possible combinations of the B and D genes... it could combine with the B and D genes when it was either dominant or recessive. That alone would give you 18 different genotypic possibilities... And if it is able to influence color, you would then have at least 8 different possible coat colors for the doberman... Does this sound logical to ANYONE?
If there has somehow been an awesome discovery of some new gene that determines color, it's a well kept secret! I've searched high and low and can't find any evidence that any such discovery has been made...
So, being a student of science, I have made my conclusions based on what I know of genetics, what I have been able to find in reputable sources (peer reviewed journals, etc) online, and on Ockham's Razor. Ockham's razor states that the simplest explanation is the best explanation. Thus, isn't it much more likely that all white dobermans are albinos based on known facts about the dog's genome and patterns of inheritance that have been studied since the 1860s? Isn't the possibility of some mysterious third gene that breaks the laws of Mendelian genetics (and by some crazy conspiracy of the country's top universities is being kept a secret) far more complicated and unlikely?
Everyone is free to make up their own mind... If you choose to believe the latter, it is your choice, but until I am shown hard scientific evidence that contradicts what I have been taught is true, I will not be convinced.
