The screw tail gene (aka DVL2) is the gene responsible for the cork screw tail in French and British Bulldogs, and Boston Terriers. It has been proven that this gene is the link to the presence of hemivertebrae in these breeds. The gene causes the tail vertebrae to be deformed (called hemivertebrae), which allows the tail to curl around on itself. Unfortunately, the deformed vertebrae are not limited to the tail, and can also occur anywhere along the entire spine, causing twists and instability.

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It is widely accepted that vertebral abnormalities have an extremely high degree of heritability meaning that if the parents are affected, the offspring are very likely to be affected. In fact, up to 93.5% of French Bulldogs have been found to have vertebral abnormalities along the entire length of their spine. It is important to note that these vertebral abnormalities can vary in number and location, and there is no way to predict how pups will be affected. Some of these abnormalities in the spine will have little consequence to the health of the dog whilst others will have a severe impact resulting in pain, paralysis and even death.

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Until recently, researchers believed that all Frenchies have 2 copies of the DVL2 gene (called homozygous). However, through genetic screening, a handful of dogs have been identified as having only a single copy (called heterozygous or carriers). This means that it is now possible to breed this gene out of the population. From recent research studies, there is a very high likelihood that the DVL2 gene also causes heritable heart defects and increases the degree of Brachycephalic Obstructive Airway Syndrome (BOAS) through the morphological changes the gene causes on the skull.

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So what does this all mean? It means that Frenchies with one or no copies of the DVL2 gene should have no hemivertebrae in their spine, although some will still have kinks in their tails. YES! They will have a fully functional tail! A normal spine also means a longer spine, so their body will be longer and should not have a roached appearance.