There are many ways in which dogs can have a characteristic coat that identifies them.
For example, have you ever wondered why some dog breeds have longer hair than others?
There are many reasons, of course. Because they are breeds from cold environments, because it helps them hunt or fight, because you don’t want your cousin, who is allergic to animals, to come to your house…
But if we had to summarize it in a single idea, it would be because genetics dictate it.
Dog Breeds with Long Hair and Their Genetics
When we talk about dog breeds with long hair, we probably think of the Afghan Hound. Its coat measures between 30 and 45 centimeters, with areas that can even be longer, such as the legs and tail.
It’s also true that it is a fairly tall breed of dog. Males can reach up to 70 centimeters in height with no problem.
However, if we did it in proportion to size, perhaps the winner would be another breed of dog, the Shih Tzu. This small dog, which barely reaches 30 centimeters in height at times, can have a coat of 20 to 25 centimeters on its body.
Such a mane is worn by only some dogs, as owners opt to cut it. The Shih Tzu breed has dense hair that requires regular care, and leaving it uncut would result in problems.
Another breed worth mentioning is the Komondor. Its hair reaches 20 to 27 centimeters in length, but it has the heaviest coat of all the dogs. It’s the winner in the list of dog breeds with heavy coats.
Considering that males of this breed weigh between 50 and 60 kilograms, it’s not too surprising.
Hairless Dog Breeds
On the other hand, we have breeds that are the exact opposite. They are breeds that practically lack a coat.
Among these breeds, perhaps the most remarkable is the Xoloitzcuintli. Although some of the most unique dog breeds are “recent,” the Xoloitzcuintli or Xolo is a dog with more than 3,000 years of history.
Its genetics are interesting. They have a phenotype of ectodermal dysplasia, with a monogenic autosomal semidominant inheritance.
That is, a single gene, located on a non-sex chromosome, is responsible for the absence of hair. The dominance is not complete, it’s partial, which is why this breed of dog retains some hair on the head and tail.
The responsible gene is the Hr variant in the FOXI3 gene.
Fun fact: This genetic variant also affects the teeth. That’s why the Xolo breed can have incomplete dentition, which doesn’t affect its quality of life.
If the animal is heterozygous, with one hairless and one hairy copy, it won’t have hair. If both copies are hairy, it will have hair. And if both copies are hairless, it won’t reach gestation, because it needs at least one hair copy to develop.
In a cross of two hairless Xolos, statistically one in every four pups would have normal hair.
Another pre-Columbian breed is the Peruvian Hairless Dog or Viringo Peruano. It shares ancestry with its Mexican cousin, and the genetic cause is also the Hr locus. However, these two breeds separated hundreds of years ago, so the mutations they present are different.
To finish this list of natural hairless dogs, let’s mention the Chinese Crested. The genetic reason again is the FOXI3 gene, and the absence of hair remains the dominant characteristic.
It’s interesting that the hairless breed from China has the mutation in the same gene as the pre-Columbian American breeds.
Some theories consider that all these breeds come from a common version of the African hairless dog, which reached both regions thousands of years ago and evolved divergently thereafter. This would explain why they share the same gene.
Others believe it was simple coincidence that the mutation, not being harmful in the heterozygous form, emerged. This would explain why they are distinct mutations in the same gene.
If we go to the top of the American continent, and place ourselves closer to the present, we have the American Hairless Terrier.
Its history is much simpler. It comes from a female of the American Rat Terrier without hair. Some of her pups also had no hair, and they started breeding among themselves to establish the breed.
Unlike the others, in this case, the responsible gene is SGK3. Another difference with the others is that the responsible mutation is recessive: the animal needs to have both hairless variants to be completely hairless.
That’s why in this case, we would talk about a completely artificial breed, created through modern crosses to form the current animal.
Genetics in Dog Coat
Within the genetics of dogs with normal coats, the FGF5 gene has been associated with the phenotype of long hair in multiple mammal species, including dogs.
This gene, whose full name is Fibroblast Growth Factor 5, encodes a protein that participates in hair growth and its regulation. In adults, this is its only known function.
And in that function, it is essential.
Therefore, when there are mutations in the gene that deactivate it or prevent it from working properly, animals have longer hair than their normal counterparts.
These mutations are mostly recessive, so the dog needs two copies to have an impressive mane.
It seems that these mutations causing long hair have no other negative or harmful effect on the animal. Studies have even been conducted to block the expression of this gene as a treatment for baldness.
There are other well-known genes in relation to dog coats, which modify it in different ways other than its length.
The KRT71 gene encodes a type II keratin protein. Some mutations cause curly hair in both dogs and cats, with the most representative breed being the Devon Rex cat.
To mention one last interesting gene, we have the RSPO2 gene. This gene is an activator of the Wnt/β-catenin pathway, a highly important cellular signaling route. It participates in multiple cellular processes and embryonic development.
Additionally, it has a mutation that produces longer and more defined hairs found on the face, such as the whiskers, beard, and eyebrows. It is a dominant variant and we can find it, for example, in Schnauzers.
There are many genetic variants in a dog’s coat. Each of them contributes its influence to the final coat.
The maintenance and care of long hair in dogs vary depending on the breed, and should be taken into account. The genetic test for pets from Koko Genetics will show you the genetic variants that make your dog have long hair.