Genetics of the Tail
Stumpy breeders refer to the types of tails as 'rumpy', 'typical', and 'LT' (long tail).
A 'rumpy' is a tail with the vertebrae so short that in many cases, you cannot palpate the end of the last vertebra. All that exists is a tuft of hair over the anus. The 'typical' Stumpy tails range from a single vertebra to up to 4 inches in length. Tails longer than 4 inches are referred to as "longtails." It should be noted that even if the tail is only missing ONE vertebra from the column, the dog is still genetically considered to be an NBT animal.
Can two Long Tails produce an NBT offspring? The ACD standard has a requirement stating that the "tail should reach the hock." However, ACD bitches (who might have tails short of the standard themselves) can occasionally produce a 'typical' bob-tailed pup. Could it be that some ACDs are in fact carrying an NBT gene? It would be very interesting to do a DNA test on some of the ACDs that tend to have less than hock-length tails.
A shotertened version of the original Finnish study on natural bobtails is located here.
- Of the 19 breeds of dogs (in this study of over 300 animals) that are born with Natural Bob Tails (NBTs), all breeds showed the allele for the trait at the same location in the gene sequence.
- Yes, it is possible for two NBT parents to produce tailed pups. The NBT is a single dominant trait. Since both parents carry one alelle for long tail and one alelle for the NBT, tailed pups can be produced.
- Breeding two long tails together should only produce LONG tails.
- No, you cannot produce a pup that is homozygous (carries two genes) for the NBT. A pup that carries two genes (one from each parent) is a lethal combination; the embryo is reabsorbed by the bitch, or the pup dies shortly after birth, if it is born.