Chondrodystrophy Type 1 IVDD (CDDY) indicates a short-legged phenotype, as well as abnormal and premature degeneration of interverebral discs leading to increased risk of intervertebral disc herniation. This means that the dog will have short legs and a stiffened spine - the spine of which may go on to degenerate, even in young dogs, causing inflammation, hemorrage, severe pain, and neurological problems. Inheritance is autosomal dominant for intervertebral disc disease, but semi-dominant for height. There are a number of breeds currently undergoing research related to this condition, and a comprehensive study in 2019 investigated breed distribution of the mutation. Understanding the allele frequencies is key to recommendations in testing and how to use test results. "For those breeds in which CDDY has been documented to segregate, in other words, both the CDDY allele and the normal allele are present in the breed, genetic testing is recommended. The results of this test can assist in breeding decisions and should be shared with the animal?s veterinarian to assist in clinical decisions. The CDDY allele has been found to be present in mixed breed dogs and therefore testing is recommended for these animals as well. For breeds where the CDDY allele is fixed in the population, in other words only the CDDY is present or allele frequency is 1.0, genetic testing for CDDY is not necessary, in these cases it is reasonable to assume that all dogs in that breed will be homozygous for CDDY (CDDY/CDDY)." [UC Davis/VGL, 2020] A current list of mutation frequency can be found from VHL:
. Other GTPs may also be able to provide frequency of muation information.