Chondrodysplasia

     Chondrodysplasia is a genetic deformation disorder which can result in crippling deformities.  Often mislabeled as "dwarfism", this condition is actually presented as abnormally short and deformed limbs.  In some dog breeds, such as dachshund and basset hound; these leg formations are "normal", and is controlled within the breed and an identical degree of impact.
     When chondrodysplasia occurs in other dog breeds, however, it can be crippling and can be found in association with other problems, such as deafness and shortened lifespans.  In the general dog population, chondrodysplasia can occur in varying degrees.  With the main focus being the front legs, chondrodysplasia can range from appearing "nearly normal" to crippling with all legs severely deformed.
     Chondrodysplasia is a simple autosomal recessive gene. To produce a chodrodysplasitic offspring both parents must be carriers.

     The following charts illustrate the genetic process of simple autosomal genes.

     Each dog has 2 genes for these characteristics: (one from the mother, one from the father).  Using D to represent a Dominant characteristic and r to represent a Recessive characteristic we have the following possibilities:

1) Dominant father (chondrodysplastic clear)
    recessive mother (chondrodysplastic)

     None of the offspring will appear to have the recessive (chondrodysplastic) fault. All of the offspring are carriers.

2) Dominant Father (chondrodysplastic clear)
    Carrier mother (appears normal but has the recessive gene)

     Half of the offspring are normal and do not carry chondrodysplasia, while the other half of the offspring appear normal but carry the recessive (chondrodysplasia) gene.

3) Carrier Father (appears normal, but carries the recessive gene)
    recessive mother (chondrodysplastic)

     Half of the offspring appear normal, but carry the recessive (chondrodysplastic) gene. The other half of the offspring are chondrodysplastic.

4) Carrier Father
    Carrier Mother

     One-quarter (1/4) of the offspring are normal and do not carry the chondrodysplastic gene. One-half (1/2) of the offspring appear normal, but carry the recessive (chondrodysplastic) gene. One-quarter (1/4) of the offspring are chondrodysplastic.

5) Recessive Father (chondrodysplastic)
    Recessive Mother (chondrodysplastic)

     All offspring are chondrodysplastic.

6) Dominant Father (chondrodysplastic clear)
    Dominant Mother (chondrodysplastic clear)

     All puppies are normal and clear of carrying the chondrodysplastic gene.

     There are several steps in the elimination of the recessive gene from a breed gene pool:
1) All chondrodysplastic animals are sterilized.
2) All animals producing a chondrodysplastic pup are sterilized.
3) Littermates of all known carriers either undergo a test breeding to determine if they are carriers or are sterilized.


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