Sometimes we see dogs with long coats who have mostly short-haired dogs in their ancestry. This can certainly be surprising for pet parents!
In most dogs, coat length is controlled by a single gene, called FGF5. Long hair is a recessive trait, which means that the variant of FGF5 coding for a long coat needs to be inherited from both parents. However, this also means that two short-haired dogs can produce long-haired puppies if they both carry for this trait.
Though it’s surprising, the variant for a long coat is present at a low frequency in many breeds we think of as being short-haired. For example, did you know there are long-haired Dalmatians and Pointers? Even many bully breeds, such as American Pit Bull Terriers and French Bulldogs can rarely carry for or have long coats, though it’s not to breed standard.
What does this mean for your dog? A dog with a lot of short-haired breeds in their mix could still happen to inherit a long coat, even though it’s unlikely. This is part of why it’s so difficult to visually identify what breeds are in a dog.