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White Coat Color Genetics

 

FOREWORD: This article may be reproduced or republished in whole with permission from Karin Rice/Rice's Miniature Schnauzers copyrighted:03/07/2006

Coat Color Inheritance in the White Miniature Schnauzer by Karin Rice

White Miniature Schnauzers have been in existence for over 100 years ever since the breed’s early beginnings in the late 1800’s. They were not “re-introduced” by crossing to Westies as some people claim by their fictitious pedigrees, but are simply a product of the early cross breedings with smaller breeds to bring the size down on the standard schnauzer. Anytime one established breed is crossed with another, for whatever reason, part of that breed’s characteristics are inherited through the DNA structure whether it be color, structure, working ability, temperament, disease, or any other inherited trait.

The only way to PROVE a dog is, or is not, carrying a certain inherited breed trait is by DNA testing, and NOW the test is available.

From my pedigree research the "white" (gelb or "yellow" as it was called in early German records) gene was introduced into the Miniature Schnauzer breed mainly through a German black Champion Miniature Schnauzer named Peter V Westerberg (PZ604) born in Nov. 1902. Peter was obviously carrying one "e" gene because it is recorded that he was bred to a female named Gretel VD Werneburg (PZ1530) (color unknown) and produced a "yellow" female pup named Mucki VD Werneburg (PSZ 8) born October 1914. Mucki was bred to a grandson of Peter named Pucki VD Werneburg, a dark S&P PSZ12 who produced the black German Champion Peterle VD Werneburg, PSZ11 born 06/02/1916 who also had to have the "e" gene since his dam was yellow.

Peter V Westerburg or his grandson, Peterle, can be traced to in every Miniature Schnauzer line I have researched. For example, if you trace every ancestor in the 5th generation of Dorem Display you will find every dog goes back to Peter Von Westerberg. With so many linebred crosses it is statistically impossible to eradicate the "white" "e" gene by visual appearance alone. Those former claims that the “white” gene has been eradicated from the Miniature Schnauzer lines could not be proven because the DNA test was not available until now. So if you are interested to know for sure if your dog does, or does not, carry for the white coat color please see the link at the bottom of this article for information about who to contact for DNA testing.

Rice’s White Miniature Schnauzers have been involved in a genome project to determine the genotype of the white color in Miniature Schnauzers. After testing several unrelated white dogs from around the world, it has been recently proven by DNA testing that the genotype for the White Miniature Schnauzer is “e/e” at MC1r (commonly referred to as the “E” locus). “E”, normal extension of black, allows the A-series alleles to show through, and “e”, recessive red/yellow, overrides whatever gene is present at the A locus to produce a dog which shows only phaeomelanin pigment in the coat. Skin and eye color show apparently normal eumelanin, although some “e,e” dogs appear to show reduced pigment on the nose, especially in winter (snow nose), but after sunbathing in warm weather they regain the black pigment on their noses much like humans getting a tan in summer. Please understand that there are two forms of melanin (pigment) in mammals hair coats. The first is called eumelanin. The base form of eumelanin is black. Eumelanin can also appear brown (often called liver in dogs) or blue-gray. The second pigment, which varies from pale cream through shades of yellow, tan, and orange/red is called phaeomelanin. All dogs have alleles at every locus. Not all proposed alleles have been proven to exist. The generally recognized color loci in dogs are referred to as: A (agouti), B (brown), C (albino series), D (blue dilution) E (extension), G (graying), M (merle), R (roaning), S (white spotting) and T (ticking.) There may be more, unrecognized gene series, and in a given breed, modifying factors may drastically affect the actual appearance. The newest proposed locus is the K locus for dominant black in certain breeds, including the Miniature Schnauzer. Our white dogs did not possess the “d” allele, which is commonly known as the Dilution gene responsible for diluting both eumelanin and phaeomelanin pigment. This stands to reason because our white Miniature Schnauzers have black skin pigment and dark eyes. Previous testing has shown the black Miniature Schnauzer does not possess the “a/a” recessive black gene either (found in certain breeds such as the German Shepherd dog), which leads me to postulate the black color comes from the “K” locus in Miniature Schnauzers. It is also postulated that the “E” extension allele is also epistatic at the K locus to allow the black color to exhibit, with “e,e” being the full suppression of color at the K locus, as well as at the A locus thus producing a white coat. The proposed “aw” wild banded hair at the agouti “A” locus, that is thought to produce the S&P in Miniature Schnauzers has not yet been determined by DNA analysis, nor has the proposed “at” for black and tan markings that is thought to produce the B&S color in the Miniature Schnauzers. “aw” is thought to be more dominant than “at”.

Based on my past breeding experience and the current DNA research, my own postulation for the 4 FCI approved Miniature Schnauzer colors is as follows and any proposed combination of alleles will hypothetically produce that coat color listed:

 

BLACK:  aw,aw E,E K,K  or aw,at E,e K,k or at,at 

BLACK & SILVER:  at,at E,E kk or  E,e

SALT & PEPPER:  aw,aw E,E k,k or aw,at  E,e  k,k

 

WHITE:  aw,aw D,D e,e K,K or aw,at K,k or at,at k,k

Note: PLEASE KEEP IN MIND AT THIS TIME ONLY THE “ee” GENE HAS BEEN PROVEN TO EXIST IN THE WHITE MINIS, and the "d,d" has been proven NOT to exist in the whites. The rest is from my own postulations garnered from available information referenced below. This "e,e" genotype for the white miniature schnauzer proves that all of the other 3 colors CAN carry a gene for the white and also that any of the 3 colored schnauzers bred to another schnauzer of any color that is carrying one "e" gene CAN produce a WHITE puppy from that mating. Therefore, a B&S with the genotype of: at,at; E,e; k,k bred to another B&S with the same genotype CAN produce a white puppy. The statistical odds are: 50% will be: at,at; E,e; k,k, (B&S) 25% will be: at,at; E,E,; k,k (B&S) 25% will be: at,at; e,e; k,k (white) By placing the Dominant black at the K locus, mating 2 S&P’s can hypothetically never produce a black if they are truly “k,k”, but can produce a B&S or a white, as well as the S&P color. Miniature Schnauzers theoretically would have BB or Bb in the B locus to produce black and B&S colors and possibly even the S&P colors, otherwise if “bb” they would produce Brown coat colors. It has been hypothesized that at the C locus the allele would be “cch” to lighten the phaeomelanin to produce the B&S color acting upon the proposed “at”(black and tan) at the A locus. It is also hypothesized that the fading colors seen in the Blacks, B&S’s and S&P’s may be due to the graying “G” gene. These hypotheses are yet to be proven.

References: http://skyway.usask.ca/~schmutz/dogcolors.html http://www.tenset.co.uk/doggen/indexus.html http://bowlingsite.mcf.com/Genetics/Genetics.html

 

· Links to DNA Testing Services · Healthgene Laboratory (Canada) DNA Testing for Coat Color & Diseases in Dogs
Contact Information: Address:
2175 Keele St.
Toronto,ON M6M3Z4
Canada

Local: 416-658-2040
Toll-Free: 1-877-371-1551
E-mail: info@healthgene.com (Ask for the DNA test for the “e” gene in the White Miniature Schnauzer)

We would like to thank Dr. Sheila Schmutz, Ph.D., Professor of Animal Science and Poultry College of Agriculture of the University of Saskatchewan, Canada for her work on this project. We would also like to thank the HealthGene Laboratories in Canada for making this test available to the public.

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