The Dog Gene Map.

Abstract

It can be argued that the domestic dog (Canis familiaris) demonstrates the power of selective breeding more than any other domesticated species. Indeed, within the 300 or so breeds of pedigree dogs, there exists a greater range of morphological types than is seen in any other mammalian species. With regard to size and weight for example, there is at least a 30-fold difference between the Chihuahua and the Saint Bernard. The vast majority of pedigree dog breeds have been selectively bred over the last 200 years, although the origin of many of the breeds is uncertain. The first Kennel Club was established in the United Kingdom in 1873; before this time dogs were bred mainly for a range of practical functions, many of which are still evident in the names of present breeds such as retriever, deerhound, and shepherd. Over the last 100 years, the increasing popularity of dog shows has altered the pattern of breeding such that the majority of dogs are now bred largely for their appearance. The dog family Canidae is thought to have diverged from other carnivore families 50 to 60 million years ago. The family, which now comprises 34 extant species, shows a wide range of chromosome morphologies, with the diploid chromosome number varying from 2n=36 (with mainly metacentric autosomes) in the red fox (Vulpes vulpes) to 2n=78 (with all autosomes being acrocentric) in the domestic dog and also a number of wolf-like canids such as the gray wolf {Canis lupus). The chromosomal rearrangements observed in the different species have been used to deduce the phylogenetic history of the group (Wayne and others 1987a,b). Mitochondrial DN A sequences have also been used to examine the evolution of the Canidae and the origins of the domestic dog (Wayne 1993). The results demonstrate that the domestic dog is an extremely close relative of the gray wolf, with as little as 0.2% variation in mitochondrial DNA sequence between the 2 species. This contrasts with 4% variation in mitochondrial sequences between gray wolves and their nearest wild relative, the coyote (Canis latrans). The timing of the divergence of the dog from the gray wolf is