Black and Tan is a color pattern that can be found in dog breeds around the world. A Black and Tan dog is a dog that is mostly black but that has tan areas at the muzzle, eye brows, chest, and legs. It can vary greatly in expression with some very minimal black and tan dogs only having a small brown spot under the tail, while some dogs will be mostly tan with only a "saddle" of black on the back. These dogs are often called saddle tan, high tan or creeping tan but genetically it tests as black and tan, a modifier is thought to be responsible for the difference in expression. A crop out black and tan is a dog that is born with the black and tan coloring in a breed that does not normally have black and tan coloring. This can come as a great shock to a breeder.
A single gene is known to cause long haired phenotypes in mammals. This gene is fibroblast growth factor 5 (FGF5). In dogs, all long haired phenotypes are inherited in a recessive manner and while the single known mutation in FGF5 explained most of the long hair phenotypes in dogs, it was not a good match in some breeds, namely the Afghan hound, Japanese Chin, Samoyed, Silky terrier and Yorkshire terrier.
We all thought we had brindle in dogs pretty much figured out. We all knew that brindle was recessive to dominant black and dominant to wild-type (KB>Kbr>ky). Recent research however, has thrown that idea on it’s head.
Researchers have recently located mutations in dopamine receptor D4 (DRD4) exon 3 and tyrosine hydroxylase (TH) that correspond to higher levels of activity, inattention and impulsiveness in Siberian Huskies. These mutations alter the way dopamine and its precursor L-DOPA are synthesized. Dopamine functions as a neurotransmitter and is primarily involved in the reward center of the brain.