Why do some dogs never grow?

From tiny Chihuahua puppies that can fit in a handbag, to giant, fierce hunting dogs . dogs have caused scientists a headache because of their varied size.

"Dogs have the largest variety of sizes in any mammal," said biologist K. Gordon Lark of the University of Utah. "One of the big questions is where does this variety of sizes come from?".

Lark and colleagues said they found part of the answer to this question: a DNA gene that controls growth causes some dogs to stay forever.

Paris Hilton and Chihuahua dog.
(Photo: fedrelandsvennen)

To understand the clues, the researchers took DNA samples and measured the body size of hundreds of Portuguese dogs. This breed has a weight that is 3 times larger, from 11 to 33 kg. By analyzing their DNA, the researchers found a piece of the gene that is closely related to the size of the animal. This gene segment controls a hormone that helps humans and other mammals to mature from birth until puberty.

In small dogs, some variants of this gene suppress gene activity, causing it to not produce enough hormones for the dogs to grow.

Medium and large dogs do not have this type of gene. So they can grow to scary size. Some other unidentified genetic material may also bring about the size of the dog's body size.

To test the results, the researchers studied more than 3,000 dogs of 143 different species, including Chihuahua, poodle, poodle, Saint Bernard, Irish hound . In small dogs, they all found that gene sequence."All dogs under 9 pounds have this particular gene sequence," Lark said.

Dogs were purebred into domestic dogs about 12,000 years ago, and because small dogs all over the world have this gene segment, researchers believe that the genetic structure may be so old.

Small dogs will proliferate more because humans consider it a good companion."Small dogs do not chase you, do not destroy, they are small and very cute, " Lark said.

MT