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Purebred Dogs Have Their Own Genes

By Kate Ruder


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Dogs

Although it looks like a dog of ancient Egypt, the Ibizan Hound is probably a modern breed.
After traveling to dog shows around the country and collecting DNA from the contestants, scientists now report that purebred dogs have distinct genetic features that are recognizably their own.

It’s possible, then, to determine the breed of any dog simply by analyzing an anonymous sample of doggie DNA.

The finding, reported today in Science, is based on a survey of nearly 100 genetic “landmarks” that vary somewhat from breed to breed. The researchers analyzed the landmarks in more than 400 dogs belonging to 85 different breeds.

In nearly every case, each dog was most closely related to other dogs of the same breed. Genetically speaking, every Mastiff looks more like another Mastiff than a Poodle or a Beagle or any other breed.

“You can take a cheek swab and say with 99 percent accuracy what dog you’re looking at,” says Elaine Ostrander of Fred Hutchinson Cancer Research Center in Seattle, Washington, who led the study and who has been a pioneer in studying the genomes of dogs.

Ostrander and her colleagues used the genetic analysis to group dogs into related breeds. This confirmed some existing ideas about breeds but also revealed a few unexpected connections. For instance, they were surprised to learn that German Shepherds are closely related to Bullmastiffs, Rottweilers, and Boxers.

As the study was getting underway, the researchers set up booths at dog shows around the United States and took cheek swabs from dogs. Dog owners were so enthusiastic about the project that the researchers collected many more samples than they could use in the study.

“This is really the first time we’ve put together the genetics of a number of breeds of dogs,” says Robert Kelly of the American Kennel Club Health Foundation, which funds research on dog health. “This is a genetic tree that we have not had before.”

Genetic evidence shows that the German Shepherd (left) is closely related to the Boxer and Mastiff (center, right).

Identifying related breeds based on genetics could help researchers hunt for genes that cause disease in dogs, some of which have counterparts in people. Most dog breeds have been created by humans over the past 300 years, and  each breed has clearly defined standards for an animal's behavior and physique.

Purebred dogs have over 350 inherited disorders including cancer, heart disease, and epilepsy. Many disorders in dogs closely mimic diseases that afflict humans.

Based on their genes, the study’s 85 breeds were classified into four groups. One group includes Mastiffs, Bulldogs, Boxers, and German Shepherds. Another includes herding dogs, such as Collies and Shetland Sheepdogs, but also Greyhounds and Saint Bernards.

The third and largest group includes dogs that have relatively recent European origins. These mainly include types of hunting dogs, terriers, pointers and retrievers.

The fourth group included the Chow Chow, Siberian Husky, and Lhasa Apso. These are probably the oldest breeds of dogs and share a common origin from Asia and Africa . This finding confirms the idea, proposed in 2002, that ancient dogs originated in Asia and over time migrated with their owners to Africa and across the Bering Strait to the Arctic .

There were some surprises. The Ibizan Hound and Pharaoh Hound, typically considered some of the oldest dog breeds, were not included in this ancient group. These breeds were thought to descend directly from Egyptian hounds that were pictured in cave drawings 5,000 years ago.

Instead, the authors say, these breeds were probably recreated from other breeds by humans in modern times. “Although their appearance matches the ancient Egyptian…hounds, their genomes do not,” they write in Science.

“Everyone wants to say that their dog was pictured on the caves of ancient Egypt ,” says Kelly. “But pharaoh hounds probably have more modern origins than people would like to admit.”

For more news visit GNN’s Dog Page.

Parker, H. et al. Genetic Structure of the Purebred Domestic Dog. Science 304, 1160-1164 (May 21, 2004).

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