German Shepherd Coat Color Geneteic Code

Canine Color and Coat Code

DNA is like a corkscrew ladder, each rungs (steps) on the ladder has four different types called; adenine (abbreviated A), cytosine (C), guanine (G) and thymine (T).  The information which DNA provides is determined on how those types are in order. Just like the binary system in a computer, the numbers 1 and 0 tells the computer on how to function; A,C,G & T in DNA,  tells the cell how to function. The information within the adjacent rungs is read by a messenger called RNA that is connected to a triad of rungs. This triad tells the cell to "start here" and "end here" which marks off certain regions of the DNA we call discrete genes. Each triad is an amino acid that becomes a chain that makes up a protein. There are also genes which tell the cell when to turn on or off another gene.

Within the DNA molecule we have chromosomes, in the central part of the cell. These chromosomes are arranged in pairs, one from the father and one from the mother. The code for a particular protein is always located in the same place on the same chromosome called a locus (plural loci). There are slightly different genes for the same protein that fit into the same locus. Each one of these genes is called an allele. Each locus will have one allele from the mother and one from the father.

When a canine makes an egg or sperm cell, they go through a process which makes only one copy of each chromosome. Unless two genes are on the same chromosome, the selection of which allele (gene) is strictly random. So if a female has one gene for black and one for brown, she will only produce black pigment or brown pigment, not both. If he's a male, then 50% of his sperm would be black pigment and 50% would be brown pigment.

Genetics has an entire language of its own; each color code comes in a set of series which determines where the pigment is placed, intensity of the pigment, whether it's diluted, and the ability of the pigment to form. These codes are written using capital letters (dominant gene) and lower case letters (recessive gene) to determine the makeup of the genes. Without going into a very detailed discussion on how these genes interact with each other I will give you a chart describing each series.

Agouti Series: this gene controls the distribution of black pigment on the body which gives the GSD their patterns.  The listed allele is in order of dominance.

At each locus a dog carries two genes, one from the dam and one from the sire. If the GSD inherits an "a" from both parents, then he/she will be solid black. If the puppy inherits an "a" from the sire and something else from the dam, then only the gene from the dam will be visible because "a" is recessive to all others. The dominant gene always works like this through the whole chart;
a + a = black (self color)
a + at = bi-color (tan point)
a + as = black and tan (saddle)
a + aw = sable (agouti)

at + a = bi-color (tan point)
at + at = bi-color (tan point)
at + as = black and tan (saddle)
at + aw = sable (agouti)

as + a = black and tan (saddle)
as + at = black and tan (saddle)
as + as = black and tan (saddle)
as + aw = sable (agouti)

aw + a = sable (agouti)
aw + at = sable (agouti)
aw + as = sable (agouti)
aw + aw = sable (agouti)

I left "ay" out of the chart because they are very rare or nonexistant in German Shepherds. You can easily see how they would work if they did turn up.

There are a few practical conclusions that you can draw from this chart:

sables can carry any other color and still be sables

a sable that has two "aw" genes can only pass on "aw" to its offspring... since "aw" will dominate all of the other possible genes the puppies could inherit from their other parent, they will be sables

two black and tans can never produce a sable (since if one of the parents had an "aw" gene to pass on, it would itself be a sable

two blacks can only produce blacks

 (Note: White is not part of this series at all. Questions about white being recessive to black, etc., have no real meaning since it is something determined at a completely different locus.)

B Series - controls the ability to produce the black pigment.

C Series- This gene effects the intensity of pigment produced.  Some believe this is the gene responsible for producing solid white. 

D Series- Controls the intensity of black pigment.

 E Series- Extension series

Dogs with the ee genotype have the black pigment in their coat fade out by the time they are 2 years old. It doesn't affect the pigment of the nose or pads. Many people confuse this with a golden sable, the difference is a golden sable dog will have a black tip at the end of its tail an ee dog has a red tip to it's tail.

Int Series- Controls the intensity of tan markings 

The genes above are the major players in determining coat color in our breed.  There are other ones out there, such as a gene that causes the salt and peppering down the backs of black and tan dogs (thought to be caused by a recessive allele). 

While it is not a color trait, the length of a dog's coat is of interest to many. It has recently been demonstrated that in many breeds, the gene FGF5 is responsible for whether a dog has a long coat (rough or fluffy), or a short (smooth) coat.