Bred to combine the loyalty of a Labrador retriever with the low-allergy coat of a poodle, they've become one of the most popular designer dogs in the world.

But not all labradoodles are half Lab and half poodle as the name given to the original puppies suggests.

One group, known as Australian labradoodles, is more poodle than Lab, according to research published today in the journal PLOS Genetics.

"We were surprised by that, we thought we would find a much more balanced representation," said study co-author Elaine Ostrander of the National Institute of Health in the US.

The fact that it's not balanced, shows how the genome has been shaped by selective breeding over just a few generations.

"Poodles elicit a lot less of an allergic response than many, many other dogs," Dr Ostrander said.

"That seems to be the trait that people want ... so that's what the breeders are putting in."

What's in a name?

The labradoodle was not originally developed for its looks.

Its inventor Wally Conron crossed a purebred white Labrador retriever with a standard poodle in the quest to breed a hypoallergenic guide dog.

There were three puppies from the cross but only one, called Sultan, was sufficiently hypoallergenic.

Wally came up with the name "labradoodle" as a way of marketing the other puppies that didn't make the cut.

"It was a gimmick. They were a crossbreed, nobody wanted them, but everybody wanted a labradoodle. Same dog, different name," he told RN's Sum of all Parts last year.

The plan was hugely successful, which Wally would later regret, raising concerns about the quality of the breeding process.

Today the lovable dog comes in at least 14 different colours, three different sizes and three different coat variations.

And there are two groups of labradoodles: first generation pups that are the direct offspring of a Labrador-retriever and a standard poodle; and the Australian labradoodle.

The Australian labradoodle, which was actually developed by US breeders, is a carefully guarded mix of several different breeds including the Labrador-retriever, poodle, English cocker spaniel, American cocker spaniel, and Irish water spaniel.

So what does the genetics tell us?

By comparing the two groups, Dr Ostrander and colleagues were able to see what was in the genome of the Australian labradoodle, and how fast it had evolved from first-generation animals and founding breeds.

They analysed the DNA of 21 pedigree Australian labradoodles in the US that were between 4 and 10 generations removed from the original poodle and Labrador parents.

While first-generation dogs were a neat 50:50 split of Lab and standard poodle, the bulk of the Australian labradoodle genome contained poodles of all sizes, a dash of Lab and a hint of American cocker spaniel.

"We knew that there was poodle and Lab, but we wondered if there were other things in there like Portuguese water dogs, and we found by and large there was not," Dr Ostrander said.

The dominance of poodle genes in the mix reflects breeding programs that have reintroduced poodles to later generations of labradoodles.

This is what you would expect if the breeders were selecting for the coat gene, said Clare Wade, an animal genetics expert from the University of Sydney.

"By that very strong selection for that characteristic you get all the other bits and pieces that come along for the ride so you end up with a predominance of poodle in the mix," Professor Wade, who was not involved in the research, explained.

Is the Australian labradoodle a true breed?

Most people are likely to have first-generation labradoodles, which are exactly what they say on the box: a cute Labrador-poodle cross.

But fans of the Australian labradoodle are lobbying for it to be officially considered a breed.

Dr Ostrander said the latest research gives them a "really strong argument."

To be classified as a breed the dog must meet a range of genetic criteria.

"The Australian labradoodle meets those criteria.

"When you cross an Australian labradoodle with an Australian labradoodle you get reproducibly something that's got all the key features of an Australian labradoodle," she said.

In other words, later generations of puppies look exactly like their parents.

While first-generation puppies all look the same, the genetic makeup of subsequent generations can be a bit of a "dog's breakfast" until the line stabilises again, Professor Wade said.

"Having a breed means there's a certain amount of predictability," she said.

"When you breed them together you'll get another one that looks like them and you can probably have some idea about what their personality and trainability is going to be like," she said.

Below | The first ever litter of labradoodle pups