Pint-Size Pups

From SuperScience, October 2007

Pint–Sized Pup (Photo: Jensen Larson)

With a height of only 12.7 centimeters (5 inches), Dancer the long–haired Chihuahua is one of the world's smallest dogs. Scientists at the National Institutes of Health in Maryland have discovered one of the reasons dogs like Dancer stay so petite.

The scientists studied the DNA of 143 different breeds of dogs. DNA is a chemical that contains information about the inherited characteristics of an organism. The scientists found that all small dogs, such as Chihuahuas, have a specific section of DNA that is only rarely found in large dogs like Great Danes.

This section of DNA may help to slow the dogs' growth. As a result, dogs that have it stay small.