Ya?l: I was walking my cocker spaniel this morning, and we ran into two other dogs---a great dane almost as tall as I am, and a tiny Chihuahua! I can't believe they are all the same species!

Don: You know, scientists are making great strides in understanding the genes that allow such a wide range of shapes, sizes and personalities in different dog breeds. Did you know domestic dogs were bred from wolves about 15,000 years ago?

Y: That's pretty recent in evolutionary terms, isn't it?

D: Very! Humans have sped up the diversification of dogs by selecting for particular physical or behavioral traits such as size, coat type, trainability, and hunting or herding ability.

But dogs still show greater variety than any other domesticated animal, and for a long time this variance has largely been unexplained.

A group of genetics researchers collaborated with dog breeders and veterinarians to study the DNA from 148 different dog breeds. With such a large sample of genes from very different kinds of dogs, they were able to identify regions in the dog DNA that are important in regulating some key traits that differ between breeds.

Four regions were found that may regulate life span, a breed characteristic that usually decreases with increasing body size. Regions associated with some behavioral stereotypes like herding, pointing and boldness were also identified.

Y: What can they do with this information?

D: The study could have far-reaching benefits for dogs and their owners. With further research, dog owners and vets could use this information to customize the care, diet and medicines to the particular needs of their breed, and to identify and perhaps prevent breed-specific diseases.