How was a three-pound toy poodle, for example, bred from a wolf growing to 40 kg or more?
The trick could be easier than you think.
The growth of dogs is regulated by about 20 different genes, but one of them is clearly the most important. It produces an insulin-like growth factor that mediates the effects of growth hormone.
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Now, an international team of researchers found two versions of its regulatory area that largely explain the differences in size between dogs and other canine animals.
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Of the versions, one results in a reduction in body size and an increase in size from both parents, the researchers report in Current Biology.
The downsizing version is prevalent in dog breeds under 15 pounds. In contrast, breeds over 25 pounds are dominated by the magnifying version, as are wolves from the northern continents.
There is a latent version of the current wolves. It was also hidden in large glacial wolves, surviving DNA from the bones of ancient wolves. So dog breeders had something to draw from.
Although the current-looking dogs and their dwarf breeds have not been bred for much of the last couple of hundred years, the ancient range of regulation has been excellent.
For example, the 40-pound Giant Schnauzer has an almost exclusively magnifying version and the Toy Poodles have a reducing version.
Both have 25-pound big poodles. For the most part, the slightly smaller 16-pound Schnauzers have only a downsizing version. An even more dominant shrinkage version of the gene is in eight-pound dwarf schnauzers and seven-person dwarf poodles.
In fact, the diminishing version evolved earlier than the diminishing one, the researchers conclude.
Namely, it prevails in all small-sized dog species. In addition, it occurs elsewhere in the line of development of predators, such as pandas, gnats, and cats.
Apparently it wasn’t until the ice age that the scaling-down version sank into the wolves and the magnifying one came to power. During the cold season, the bulky, slowly cooling carcass became an advantage.
Published in Science Nature 3/2022.
Source: Tiede by www.tiede.fi.
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