A Report from the Animal Health Trust
Gene for Short-Tail (Bob-Tail) in Dogs

Note in Sweden they are referred to as stubb tails not bob tails.

A gene causing short-tails (or "bob-tails") has been identified and published in the scientific literature in 2001. Subsequent research (reported in 2009) has extended the number of breeds having this short-tail form of the gene, although not all breeds with short-tails show this genetic change (mutation).
Research was carried out on the Swedish Vallhund starting late 2010.

The mutation causing the trait is in a gene called a T-box transcription factor involved in development of the embryo.

The test applies to Pembroke Welsh Corgis and to Australian Shepherds as well as several other breeds e.g.(Swedish Vallhund). In the breeds covered, the test can be used to confirm that an individual dog has a naturally short-tail, rather than a docked-tail.

Results are as:
CLEAR: the dog has two copies of the normal form of the gene and no copies of the short-tail form of the gene and will show a longer tail

ONE COPY: the dog has one copy of the normal form of the gene and one copy of the short-tail form of the gene and will show a short (bob)-tail.

So far, no dogs with two copies of the short-tail form of the gene have been reported, and it is believed that the embryos do not survive and that no pups with this genetic status are born.

Therefore, all dogs with one copy of the short-tail gene and one copy of the normal form of the gene will have a short-tail, dogs with two copies of the normal form of the gene will have a long-tail, unless other factors are involved.

Haworth,K., Putt,W., Cattanach,B., Breen,M., Binns,M., Lingaas,F., Edwards,Y.H. (2001) Canine homolog of the T-box transcription factor T; failure of the protein to bind to its DNA target leads to a short-tail phenotype. Mammalian Genome 12 212-218.
Hytönen,M.K., Grall,A., Hédan,B., Dréano, Seguin,S.J., Delattre,D., Thomas,A., Galibert,F., Paulin,L., Lohi,H., Sainio,K. and André.C. (2009) Ancestral T-Box Mutation is present in many, but Not All, Short-Tailed Dog

If you would like to have your dog tested a variety of labs run the bobtail gene test such as ADD