Among these, a retrocopy of fibroblast growth factor 4 (FGF4) shows a strong association with a chondrodysplasia phenotype (characterized by short limbs) and is a major genetic factor underlying both this morphology and a high prevalence of intervertebral disc disease (IVDD) in certain dog breeds [105, 106]. Here, FGF4 is linked to chondrodysplasia.