Your dog may have hidden coat colours and traits lurking beneath

31 Oct 2019

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Ever wondered why a pure-bred puppy looks a little different to the others? There may be a scientific reason for that.

A pure-bred dog is often seen as the most prized among dog owners, but every so often a puppy can look quite different from the rest of its siblings. Rather than this dog being a mutt, researchers from Purdue University’s College of Veterinary Medicine have discovered that some breeds may have hidden coat colours lurking underneath.

In a paper published to Plos One, the researchers, led by Dr Kari Ekenstedt, examined the genetics of 212 dog breeds and used standard breed descriptions from major US and international dog breed registries to determine coat colours and tail lengths that were accepted within each breed.

“These are pure-bred dogs with traits that their breed clubs say they’re not supposed to have,” said Ekenstedt.

“The message of this paper is: ‘Hey, these gene variants exist in your breed, and if a few dogs are born with these traits, it’s not caused by accidental breeding and it’s not a mutt; it’s a pure-bred showing this known genetic potential’.”

The researchers said genetic data used in the study revealed a lot of unexpected information. Coat colour genes have a significant amount of epistasis between them, meaning that what happens at one gene can mask what’s happening at another gene.

Because of epistasis, it’s rare to see those masked genes actually expressed in a dog’s coat colour.

Barking up the wrong family tree

An example they gave of a ‘fault’ allele – a gene variant that could result in a trait not seen with a particular dog breed – is one that results in a brown colour in both hair and skin. While a brown colour is permitted by dog breeding groups in a Labrador retriever, for example, breeds such as the Rottweiler and German shepherd with a brown colour are not. This results in a lower frequency of brown alleles.

When it comes to traits, there are 18 recognised breeds of dogs that have the genetic potential to be born without a tail, such as the Australian shepherd. But the data shows that up to 48 of the breeds analysed – including the dachshund – possess the tailless gene variant, usually at a very low frequency.

Dr Dayna Dreger, one of the researchers on the study, commented: “A breeder would certainly be surprised to see a dachshund born without a tail. The chances are low, but our research shows that the potential is there.”

She hopes that their discovery will prompt a discussion among dog breeders about their decision-making process and whether an animal counts as a pure-bred or not.

“There’s an assumption that the standards for these different breeds of dogs are set in stone,” Dreger said.

“People will often make assumptions that if it doesn’t match this, it’s not pure-bred. This data shows that there is a lot of variation in some of these breeds, and the standards are not as concrete as we expect them to be.”

Colm Gorey was a senior journalist with Silicon Republic