CHICAGO: A single genetic mutation explains why dogs vary in size from the miniature Chihuahua to massive mastiffs, a range unmatched by any other mammal, according to a study released Thursday.

Researchers have long puzzled over the tremendous variation in size seen in canine breeds, particularly since the species diversified over a relatively short period of time from an evolutionary standpoint. The new study suggests the riddle can be explained by a combination of a genetic accident that created a small dog and ten thousand years of selective dog-breeding that ensured the rapid dissemination of this particular piece of doggy DNA. The researchers believe the discovery of the DNA mutation could also help explain why humans vary so much in size.

“The study is a major milestone in canine genetics. We have precisely located the major gene that produces our miniature breeds,” said study co-author Paul Jones, a genetics researcher at Mars Inc, the US confectionery and pet food giant which supplied DNA samples used in the study.—AFP