Hessen German Shepherd Dogs - Est. 1981




Degenerative Myelopathy (DM) Risk in Dogs
A Layman's View


Each dog carries 2 copies. These are the possible combinations:

N/N = Clear (2 copies of the Normal allele)
N/C = Carrier (1 Normal allele/1 DM mutation)
C/C = At Risk (2 copies of the DM mutation)

Each parent contributes 1 copy to each pup. So, At Risk "C/C" to At Risk "C/C" can only produce At Risk "C/C" puppies. Likewise, if you breed 2 Clears "N/N" & "N/N", you can only get "N/N" Clear puppies.

If you breed Clear "N/N" to At Risk "C/C", 100% of the puppies will be Carriers "N/C" - the Clear "N/N" parent can only contribute an "N" and the At Risk "C/C" parent can only contribute a "C" so the puppies can only be "N/C" which is Carrier.

It gets a little more complicated when you breed a Carrier. The possible combinations for a Clear "N/N" parent bred to a Carrier "N/C" parent are:

Dam    Sire      Pup

N / N + N / C = N / N

N / N + N / C = N / N

N / N + N / C = N / C

N / N + N / C = N / C

The following chart shows the probabilities of the offspring based on the parents' genotypes. Bear in mind that Mother Nature doesn't necessarily pay attention to the odds.  **Note that breeding 2 "N/C" Carrier parents can produce At Risk "C/C" puppies.

The above probability table also has the same odds for breeding Long Coats, Black Dogs and other genetic traits.

Black Coat Factor
axax  R96C -/- = Does not carry Black Recessive
aaR96C +/- = Carries the Black Recessive
aa  R96C +/+ = Dog is Black in Color

Long Coat Factor                      
N/N = Short Coat                       
N/F = Carries Coat Factor         
F/F = Long Coat                        

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